Added loading and error indications for web UI

4 files changed, 72 insertions, 4489 deletions

diff --git a/web/adapter.js b/web/adapter.js
deleted file mode 100644
index 6bfa37b..0000000
--- a/web/adapter.js
+++ /dev/null
@@ -1,4469 +0,0 @@
-(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.adapter = f()}})(function(){var define,module,exports;return (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
-/*
- *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
-
-var SDPUtils = require('sdp');
-
-function writeMediaSection(transceiver, caps, type, stream, dtlsRole) {
-  var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);
-
-  // Map ICE parameters (ufrag, pwd) to SDP.
-  sdp += SDPUtils.writeIceParameters(
-      transceiver.iceGatherer.getLocalParameters());
-
-  // Map DTLS parameters to SDP.
-  sdp += SDPUtils.writeDtlsParameters(
-      transceiver.dtlsTransport.getLocalParameters(),
-      type === 'offer' ? 'actpass' : dtlsRole || 'active');
-
-  sdp += 'a=mid:' + transceiver.mid + '\r\n';
-
-  if (transceiver.direction) {
-    sdp += 'a=' + transceiver.direction + '\r\n';
-  } else if (transceiver.rtpSender && transceiver.rtpReceiver) {
-    sdp += 'a=sendrecv\r\n';
-  } else if (transceiver.rtpSender) {
-    sdp += 'a=sendonly\r\n';
-  } else if (transceiver.rtpReceiver) {
-    sdp += 'a=recvonly\r\n';
-  } else {
-    sdp += 'a=inactive\r\n';
-  }
-
-  if (transceiver.rtpSender) {
-    // spec.
-    var msid = 'msid:' + stream.id + ' ' +
-        transceiver.rtpSender.track.id + '\r\n';
-    sdp += 'a=' + msid;
-
-    // for Chrome.
-    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
-        ' ' + msid;
-    if (transceiver.sendEncodingParameters[0].rtx) {
-      sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
-          ' ' + msid;
-      sdp += 'a=ssrc-group:FID ' +
-          transceiver.sendEncodingParameters[0].ssrc + ' ' +
-          transceiver.sendEncodingParameters[0].rtx.ssrc +
-          '\r\n';
-    }
-  }
-  // FIXME: this should be written by writeRtpDescription.
-  sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
-      ' cname:' + SDPUtils.localCName + '\r\n';
-  if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
-    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
-        ' cname:' + SDPUtils.localCName + '\r\n';
-  }
-  return sdp;
-}
-
-// Edge does not like
-// 1) stun: filtered after 14393 unless ?transport=udp is present
-// 2) turn: that does not have all of turn:host:port?transport=udp
-// 3) turn: with ipv6 addresses
-// 4) turn: occurring muliple times
-function filterIceServers(iceServers, edgeVersion) {
-  var hasTurn = false;
-  iceServers = JSON.parse(JSON.stringify(iceServers));
-  return iceServers.filter(function(server) {
-    if (server && (server.urls || server.url)) {
-      var urls = server.urls || server.url;
-      if (server.url && !server.urls) {
-        console.warn('RTCIceServer.url is deprecated! Use urls instead.');
-      }
-      var isString = typeof urls === 'string';
-      if (isString) {
-        urls = [urls];
-      }
-      urls = urls.filter(function(url) {
-        var validTurn = url.indexOf('turn:') === 0 &&
-            url.indexOf('transport=udp') !== -1 &&
-            url.indexOf('turn:[') === -1 &&
-            !hasTurn;
-
-        if (validTurn) {
-          hasTurn = true;
-          return true;
-        }
-        return url.indexOf('stun:') === 0 && edgeVersion >= 14393 &&
-            url.indexOf('?transport=udp') === -1;
-      });
-
-      delete server.url;
-      server.urls = isString ? urls[0] : urls;
-      return !!urls.length;
-    }
-    return false;
-  });
-}
-
-// Determines the intersection of local and remote capabilities.
-function getCommonCapabilities(localCapabilities, remoteCapabilities) {
-  var commonCapabilities = {
-    codecs: [],
-    headerExtensions: [],
-    fecMechanisms: []
-  };
-
-  var findCodecByPayloadType = function(pt, codecs) {
-    pt = parseInt(pt, 10);
-    for (var i = 0; i < codecs.length; i++) {
-      if (codecs[i].payloadType === pt ||
-          codecs[i].preferredPayloadType === pt) {
-        return codecs[i];
-      }
-    }
-  };
-
-  var rtxCapabilityMatches = function(lRtx, rRtx, lCodecs, rCodecs) {
-    var lCodec = findCodecByPayloadType(lRtx.parameters.apt, lCodecs);
-    var rCodec = findCodecByPayloadType(rRtx.parameters.apt, rCodecs);
-    return lCodec && rCodec &&
-        lCodec.name.toLowerCase() === rCodec.name.toLowerCase();
-  };
-
-  localCapabilities.codecs.forEach(function(lCodec) {
-    for (var i = 0; i < remoteCapabilities.codecs.length; i++) {
-      var rCodec = remoteCapabilities.codecs[i];
-      if (lCodec.name.toLowerCase() === rCodec.name.toLowerCase() &&
-          lCodec.clockRate === rCodec.clockRate) {
-        if (lCodec.name.toLowerCase() === 'rtx' &&
-            lCodec.parameters && rCodec.parameters.apt) {
-          // for RTX we need to find the local rtx that has a apt
-          // which points to the same local codec as the remote one.
-          if (!rtxCapabilityMatches(lCodec, rCodec,
-              localCapabilities.codecs, remoteCapabilities.codecs)) {
-            continue;
-          }
-        }
-        rCodec = JSON.parse(JSON.stringify(rCodec)); // deepcopy
-        // number of channels is the highest common number of channels
-        rCodec.numChannels = Math.min(lCodec.numChannels,
-            rCodec.numChannels);
-        // push rCodec so we reply with offerer payload type
-        commonCapabilities.codecs.push(rCodec);
-
-        // determine common feedback mechanisms
-        rCodec.rtcpFeedback = rCodec.rtcpFeedback.filter(function(fb) {
-          for (var j = 0; j < lCodec.rtcpFeedback.length; j++) {
-            if (lCodec.rtcpFeedback[j].type === fb.type &&
-                lCodec.rtcpFeedback[j].parameter === fb.parameter) {
-              return true;
-            }
-          }
-          return false;
-        });
-        // FIXME: also need to determine .parameters
-        //  see https://github.com/openpeer/ortc/issues/569
-        break;
-      }
-    }
-  });
-
-  localCapabilities.headerExtensions.forEach(function(lHeaderExtension) {
-    for (var i = 0; i < remoteCapabilities.headerExtensions.length;
-         i++) {
-      var rHeaderExtension = remoteCapabilities.headerExtensions[i];
-      if (lHeaderExtension.uri === rHeaderExtension.uri) {
-        commonCapabilities.headerExtensions.push(rHeaderExtension);
-        break;
-      }
-    }
-  });
-
-  // FIXME: fecMechanisms
-  return commonCapabilities;
-}
-
-// is action=setLocalDescription with type allowed in signalingState
-function isActionAllowedInSignalingState(action, type, signalingState) {
-  return {
-    offer: {
-      setLocalDescription: ['stable', 'have-local-offer'],
-      setRemoteDescription: ['stable', 'have-remote-offer']
-    },
-    answer: {
-      setLocalDescription: ['have-remote-offer', 'have-local-pranswer'],
-      setRemoteDescription: ['have-local-offer', 'have-remote-pranswer']
-    }
-  }[type][action].indexOf(signalingState) !== -1;
-}
-
-function maybeAddCandidate(iceTransport, candidate) {
-  // Edge's internal representation adds some fields therefore
-  // not all fieldѕ are taken into account.
-  var alreadyAdded = iceTransport.getRemoteCandidates()
-      .find(function(remoteCandidate) {
-        return candidate.foundation === remoteCandidate.foundation &&
-            candidate.ip === remoteCandidate.ip &&
-            candidate.port === remoteCandidate.port &&
-            candidate.priority === remoteCandidate.priority &&
-            candidate.protocol === remoteCandidate.protocol &&
-            candidate.type === remoteCandidate.type;
-      });
-  if (!alreadyAdded) {
-    iceTransport.addRemoteCandidate(candidate);
-  }
-  return !alreadyAdded;
-}
-
-module.exports = function(window, edgeVersion) {
-  var RTCPeerConnection = function(config) {
-    var self = this;
-
-    var _eventTarget = document.createDocumentFragment();
-    ['addEventListener', 'removeEventListener', 'dispatchEvent']
-        .forEach(function(method) {
-          self[method] = _eventTarget[method].bind(_eventTarget);
-        });
-
-    this.onicecandidate = null;
-    this.onaddstream = null;
-    this.ontrack = null;
-    this.onremovestream = null;
-    this.onsignalingstatechange = null;
-    this.oniceconnectionstatechange = null;
-    this.onicegatheringstatechange = null;
-    this.onnegotiationneeded = null;
-    this.ondatachannel = null;
-    this.canTrickleIceCandidates = null;
-
-    this.needNegotiation = false;
-
-    this.localStreams = [];
-    this.remoteStreams = [];
-
-    this.localDescription = null;
-    this.remoteDescription = null;
-
-    this.signalingState = 'stable';
-    this.iceConnectionState = 'new';
-    this.iceGatheringState = 'new';
-
-    config = JSON.parse(JSON.stringify(config || {}));
-
-    this.usingBundle = config.bundlePolicy === 'max-bundle';
-    if (config.rtcpMuxPolicy === 'negotiate') {
-      var e = new Error('rtcpMuxPolicy \'negotiate\' is not supported');
-      e.name = 'NotSupportedError';
-      throw(e);
-    } else if (!config.rtcpMuxPolicy) {
-      config.rtcpMuxPolicy = 'require';
-    }
-
-    switch (config.iceTransportPolicy) {
-      case 'all':
-      case 'relay':
-        break;
-      default:
-        config.iceTransportPolicy = 'all';
-        break;
-    }
-
-    switch (config.bundlePolicy) {
-      case 'balanced':
-      case 'max-compat':
-      case 'max-bundle':
-        break;
-      default:
-        config.bundlePolicy = 'balanced';
-        break;
-    }
-
-    config.iceServers = filterIceServers(config.iceServers || [], edgeVersion);
-
-    this._iceGatherers = [];
-    if (config.iceCandidatePoolSize) {
-      for (var i = config.iceCandidatePoolSize; i > 0; i--) {
-        this._iceGatherers = new window.RTCIceGatherer({
-          iceServers: config.iceServers,
-          gatherPolicy: config.iceTransportPolicy
-        });
-      }
-    } else {
-      config.iceCandidatePoolSize = 0;
-    }
-
-    this._config = config;
-
-    // per-track iceGathers, iceTransports, dtlsTransports, rtpSenders, ...
-    // everything that is needed to describe a SDP m-line.
-    this.transceivers = [];
-
-    this._sdpSessionId = SDPUtils.generateSessionId();
-    this._sdpSessionVersion = 0;
-
-    this._dtlsRole = undefined; // role for a=setup to use in answers.
-  };
-
-  RTCPeerConnection.prototype._emitGatheringStateChange = function() {
-    var event = new Event('icegatheringstatechange');
-    this.dispatchEvent(event);
-    if (typeof this.onicegatheringstatechange === 'function') {
-      this.onicegatheringstatechange(event);
-    }
-  };
-
-  RTCPeerConnection.prototype.getConfiguration = function() {
-    return this._config;
-  };
-
-  RTCPeerConnection.prototype.getLocalStreams = function() {
-    return this.localStreams;
-  };
-
-  RTCPeerConnection.prototype.getRemoteStreams = function() {
-    return this.remoteStreams;
-  };
-
-  // internal helper to create a transceiver object.
-  // (whih is not yet the same as the WebRTC 1.0 transceiver)
-  RTCPeerConnection.prototype._createTransceiver = function(kind) {
-    var hasBundleTransport = this.transceivers.length > 0;
-    var transceiver = {
-      track: null,
-      iceGatherer: null,
-      iceTransport: null,
-      dtlsTransport: null,
-      localCapabilities: null,
-      remoteCapabilities: null,
-      rtpSender: null,
-      rtpReceiver: null,
-      kind: kind,
-      mid: null,
-      sendEncodingParameters: null,
-      recvEncodingParameters: null,
-      stream: null,
-      wantReceive: true
-    };
-    if (this.usingBundle && hasBundleTransport) {
-      transceiver.iceTransport = this.transceivers[0].iceTransport;
-      transceiver.dtlsTransport = this.transceivers[0].dtlsTransport;
-    } else {
-      var transports = this._createIceAndDtlsTransports();
-      transceiver.iceTransport = transports.iceTransport;
-      transceiver.dtlsTransport = transports.dtlsTransport;
-    }
-    this.transceivers.push(transceiver);
-    return transceiver;
-  };
-
-  RTCPeerConnection.prototype.addTrack = function(track, stream) {
-    var transceiver;
-    for (var i = 0; i < this.transceivers.length; i++) {
-      if (!this.transceivers[i].track &&
-          this.transceivers[i].kind === track.kind) {
-        transceiver = this.transceivers[i];
-      }
-    }
-    if (!transceiver) {
-      transceiver = this._createTransceiver(track.kind);
-    }
-
-    this._maybeFireNegotiationNeeded();
-
-    if (this.localStreams.indexOf(stream) === -1) {
-      this.localStreams.push(stream);
-    }
-
-    transceiver.track = track;
-    transceiver.stream = stream;
-    transceiver.rtpSender = new window.RTCRtpSender(track,
-        transceiver.dtlsTransport);
-    return transceiver.rtpSender;
-  };
-
-  RTCPeerConnection.prototype.addStream = function(stream) {
-    var self = this;
-    if (edgeVersion >= 15025) {
-      stream.getTracks().forEach(function(track) {
-        self.addTrack(track, stream);
-      });
-    } else {
-      // Clone is necessary for local demos mostly, attaching directly
-      // to two different senders does not work (build 10547).
-      // Fixed in 15025 (or earlier)
-      var clonedStream = stream.clone();
-      stream.getTracks().forEach(function(track, idx) {
-        var clonedTrack = clonedStream.getTracks()[idx];
-        track.addEventListener('enabled', function(event) {
-          clonedTrack.enabled = event.enabled;
-        });
-      });
-      clonedStream.getTracks().forEach(function(track) {
-        self.addTrack(track, clonedStream);
-      });
-    }
-  };
-
-  RTCPeerConnection.prototype.removeStream = function(stream) {
-    var idx = this.localStreams.indexOf(stream);
-    if (idx > -1) {
-      this.localStreams.splice(idx, 1);
-      this._maybeFireNegotiationNeeded();
-    }
-  };
-
-  RTCPeerConnection.prototype.getSenders = function() {
-    return this.transceivers.filter(function(transceiver) {
-      return !!transceiver.rtpSender;
-    })
-    .map(function(transceiver) {
-      return transceiver.rtpSender;
-    });
-  };
-
-  RTCPeerConnection.prototype.getReceivers = function() {
-    return this.transceivers.filter(function(transceiver) {
-      return !!transceiver.rtpReceiver;
-    })
-    .map(function(transceiver) {
-      return transceiver.rtpReceiver;
-    });
-  };
-
-
-  RTCPeerConnection.prototype._createIceGatherer = function(sdpMLineIndex,
-      usingBundle) {
-    var self = this;
-    if (usingBundle && sdpMLineIndex > 0) {
-      return this.transceivers[0].iceGatherer;
-    } else if (this._iceGatherers.length) {
-      return this._iceGatherers.shift();
-    }
-    var iceGatherer = new window.RTCIceGatherer({
-      iceServers: this._config.iceServers,
-      gatherPolicy: this._config.iceTransportPolicy
-    });
-    Object.defineProperty(iceGatherer, 'state',
-        {value: 'new', writable: true}
-    );
-
-    this.transceivers[sdpMLineIndex].candidates = [];
-    this.transceivers[sdpMLineIndex].bufferCandidates = function(event) {
-      var end = !event.candidate || Object.keys(event.candidate).length === 0;
-      // polyfill since RTCIceGatherer.state is not implemented in
-      // Edge 10547 yet.
-      iceGatherer.state = end ? 'completed' : 'gathering';
-      if (self.transceivers[sdpMLineIndex].candidates !== null) {
-        self.transceivers[sdpMLineIndex].candidates.push(event.candidate);
-      }
-    };
-    iceGatherer.addEventListener('localcandidate',
-      this.transceivers[sdpMLineIndex].bufferCandidates);
-    return iceGatherer;
-  };
-
-  // start gathering from an RTCIceGatherer.
-  RTCPeerConnection.prototype._gather = function(mid, sdpMLineIndex) {
-    var self = this;
-    var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer;
-    if (iceGatherer.onlocalcandidate) {
-      return;
-    }
-    var candidates = this.transceivers[sdpMLineIndex].candidates;
-    this.transceivers[sdpMLineIndex].candidates = null;
-    iceGatherer.removeEventListener('localcandidate',
-      this.transceivers[sdpMLineIndex].bufferCandidates);
-    iceGatherer.onlocalcandidate = function(evt) {
-      if (self.usingBundle && sdpMLineIndex > 0) {
-        // if we know that we use bundle we can drop candidates with
-        // ѕdpMLineIndex > 0. If we don't do this then our state gets
-        // confused since we dispose the extra ice gatherer.
-        return;
-      }
-      var event = new Event('icecandidate');
-      event.candidate = {sdpMid: mid, sdpMLineIndex: sdpMLineIndex};
-
-      var cand = evt.candidate;
-      // Edge emits an empty object for RTCIceCandidateComplete‥
-      var end = !cand || Object.keys(cand).length === 0;
-      if (end) {
-        // polyfill since RTCIceGatherer.state is not implemented in
-        // Edge 10547 yet.
-        if (iceGatherer.state === 'new' || iceGatherer.state === 'gathering') {
-          iceGatherer.state = 'completed';
-        }
-      } else {
-        if (iceGatherer.state === 'new') {
-          iceGatherer.state = 'gathering';
-        }
-        // RTCIceCandidate doesn't have a component, needs to be added
-        cand.component = 1;
-        event.candidate.candidate = SDPUtils.writeCandidate(cand);
-      }
-
-      // update local description.
-      var sections = SDPUtils.splitSections(self.localDescription.sdp);
-      if (!end) {
-        sections[event.candidate.sdpMLineIndex + 1] +=
-            'a=' + event.candidate.candidate + '\r\n';
-      } else {
-        sections[event.candidate.sdpMLineIndex + 1] +=
-            'a=end-of-candidates\r\n';
-      }
-      self.localDescription.sdp = sections.join('');
-      var complete = self.transceivers.every(function(transceiver) {
-        return transceiver.iceGatherer &&
-            transceiver.iceGatherer.state === 'completed';
-      });
-
-      if (self.iceGatheringState !== 'gathering') {
-        self.iceGatheringState = 'gathering';
-        self._emitGatheringStateChange();
-      }
-
-      // Emit candidate. Also emit null candidate when all gatherers are
-      // complete.
-      if (!end) {
-        self.dispatchEvent(event);
-        if (typeof self.onicecandidate === 'function') {
-          self.onicecandidate(event);
-        }
-      }
-      if (complete) {
-        self.dispatchEvent(new Event('icecandidate'));
-        if (typeof self.onicecandidate === 'function') {
-          self.onicecandidate(new Event('icecandidate'));
-        }
-        self.iceGatheringState = 'complete';
-        self._emitGatheringStateChange();
-      }
-    };
-
-    // emit already gathered candidates.
-    window.setTimeout(function() {
-      candidates.forEach(function(candidate) {
-        var e = new Event('RTCIceGatherEvent');
-        e.candidate = candidate;
-        iceGatherer.onlocalcandidate(e);
-      });
-    }, 0);
-  };
-
-  // Create ICE transport and DTLS transport.
-  RTCPeerConnection.prototype._createIceAndDtlsTransports = function() {
-    var self = this;
-    var iceTransport = new window.RTCIceTransport(null);
-    iceTransport.onicestatechange = function() {
-      self._updateConnectionState();
-    };
-
-    var dtlsTransport = new window.RTCDtlsTransport(iceTransport);
-    dtlsTransport.ondtlsstatechange = function() {
-      self._updateConnectionState();
-    };
-    dtlsTransport.onerror = function() {
-      // onerror does not set state to failed by itself.
-      Object.defineProperty(dtlsTransport, 'state',
-          {value: 'failed', writable: true});
-      self._updateConnectionState();
-    };
-
-    return {
-      iceTransport: iceTransport,
-      dtlsTransport: dtlsTransport
-    };
-  };
-
-  // Destroy ICE gatherer, ICE transport and DTLS transport.
-  // Without triggering the callbacks.
-  RTCPeerConnection.prototype._disposeIceAndDtlsTransports = function(
-      sdpMLineIndex) {
-    var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer;
-    if (iceGatherer) {
-      delete iceGatherer.onlocalcandidate;
-      delete this.transceivers[sdpMLineIndex].iceGatherer;
-    }
-    var iceTransport = this.transceivers[sdpMLineIndex].iceTransport;
-    if (iceTransport) {
-      delete iceTransport.onicestatechange;
-      delete this.transceivers[sdpMLineIndex].iceTransport;
-    }
-    var dtlsTransport = this.transceivers[sdpMLineIndex].dtlsTransport;
-    if (dtlsTransport) {
-      delete dtlsTransport.ondtlsstatechange;
-      delete dtlsTransport.onerror;
-      delete this.transceivers[sdpMLineIndex].dtlsTransport;
-    }
-  };
-
-  // Start the RTP Sender and Receiver for a transceiver.
-  RTCPeerConnection.prototype._transceive = function(transceiver,
-      send, recv) {
-    var params = getCommonCapabilities(transceiver.localCapabilities,
-        transceiver.remoteCapabilities);
-    if (send && transceiver.rtpSender) {
-      params.encodings = transceiver.sendEncodingParameters;
-      params.rtcp = {
-        cname: SDPUtils.localCName,
-        compound: transceiver.rtcpParameters.compound
-      };
-      if (transceiver.recvEncodingParameters.length) {
-        params.rtcp.ssrc = transceiver.recvEncodingParameters[0].ssrc;
-      }
-      transceiver.rtpSender.send(params);
-    }
-    if (recv && transceiver.rtpReceiver && params.codecs.length > 0) {
-      // remove RTX field in Edge 14942
-      if (transceiver.kind === 'video'
-          && transceiver.recvEncodingParameters
-          && edgeVersion < 15019) {
-        transceiver.recvEncodingParameters.forEach(function(p) {
-          delete p.rtx;
-        });
-      }
-      params.encodings = transceiver.recvEncodingParameters;
-      params.rtcp = {
-        cname: transceiver.rtcpParameters.cname,
-        compound: transceiver.rtcpParameters.compound
-      };
-      if (transceiver.sendEncodingParameters.length) {
-        params.rtcp.ssrc = transceiver.sendEncodingParameters[0].ssrc;
-      }
-      transceiver.rtpReceiver.receive(params);
-    }
-  };
-
-  RTCPeerConnection.prototype.setLocalDescription = function(description) {
-    var self = this;
-    var args = arguments;
-
-    if (!isActionAllowedInSignalingState('setLocalDescription',
-        description.type, this.signalingState)) {
-      return new Promise(function(resolve, reject) {
-        var e = new Error('Can not set local ' + description.type +
-            ' in state ' + self.signalingState);
-        e.name = 'InvalidStateError';
-        if (args.length > 2 && typeof args[2] === 'function') {
-          args[2].apply(null, [e]);
-        }
-        reject(e);
-      });
-    }
-
-    var sections;
-    var sessionpart;
-    if (description.type === 'offer') {
-      // VERY limited support for SDP munging. Limited to:
-      // * changing the order of codecs
-      sections = SDPUtils.splitSections(description.sdp);
-      sessionpart = sections.shift();
-      sections.forEach(function(mediaSection, sdpMLineIndex) {
-        var caps = SDPUtils.parseRtpParameters(mediaSection);
-        self.transceivers[sdpMLineIndex].localCapabilities = caps;
-      });
-
-      this.transceivers.forEach(function(transceiver, sdpMLineIndex) {
-        self._gather(transceiver.mid, sdpMLineIndex);
-      });
-    } else if (description.type === 'answer') {
-      sections = SDPUtils.splitSections(self.remoteDescription.sdp);
-      sessionpart = sections.shift();
-      var isIceLite = SDPUtils.matchPrefix(sessionpart,
-          'a=ice-lite').length > 0;
-      sections.forEach(function(mediaSection, sdpMLineIndex) {
-        var transceiver = self.transceivers[sdpMLineIndex];
-        var iceGatherer = transceiver.iceGatherer;
-        var iceTransport = transceiver.iceTransport;
-        var dtlsTransport = transceiver.dtlsTransport;
-        var localCapabilities = transceiver.localCapabilities;
-        var remoteCapabilities = transceiver.remoteCapabilities;
-
-        // treat bundle-only as not-rejected.
-        var rejected = SDPUtils.isRejected(mediaSection) &&
-            !SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 1;
-
-        if (!rejected && !transceiver.isDatachannel) {
-          var remoteIceParameters = SDPUtils.getIceParameters(
-              mediaSection, sessionpart);
-          var remoteDtlsParameters = SDPUtils.getDtlsParameters(
-              mediaSection, sessionpart);
-          if (isIceLite) {
-            remoteDtlsParameters.role = 'server';
-          }
-
-          if (!self.usingBundle || sdpMLineIndex === 0) {
-            self._gather(transceiver.mid, sdpMLineIndex);
-            if (iceTransport.state === 'new') {
-              iceTransport.start(iceGatherer, remoteIceParameters,
-                  isIceLite ? 'controlling' : 'controlled');
-            }
-            if (dtlsTransport.state === 'new') {
-              dtlsTransport.start(remoteDtlsParameters);
-            }
-          }
-
-          // Calculate intersection of capabilities.
-          var params = getCommonCapabilities(localCapabilities,
-              remoteCapabilities);
-
-          // Start the RTCRtpSender. The RTCRtpReceiver for this
-          // transceiver has already been started in setRemoteDescription.
-          self._transceive(transceiver,
-              params.codecs.length > 0,
-              false);
-        }
-      });
-    }
-
-    this.localDescription = {
-      type: description.type,
-      sdp: description.sdp
-    };
-    switch (description.type) {
-      case 'offer':
-        this._updateSignalingState('have-local-offer');
-        break;
-      case 'answer':
-        this._updateSignalingState('stable');
-        break;
-      default:
-        throw new TypeError('unsupported type "' + description.type +
-            '"');
-    }
-
-    // If a success callback was provided, emit ICE candidates after it
-    // has been executed. Otherwise, emit callback after the Promise is
-    // resolved.
-    var cb = arguments.length > 1 && typeof arguments[1] === 'function' &&
-        arguments[1];
-    return new Promise(function(resolve) {
-      if (cb) {
-        cb.apply(null);
-      }
-      resolve();
-    });
-  };
-
-  RTCPeerConnection.prototype.setRemoteDescription = function(description) {
-    var self = this;
-    var args = arguments;
-
-    if (!isActionAllowedInSignalingState('setRemoteDescription',
-        description.type, this.signalingState)) {
-      return new Promise(function(resolve, reject) {
-        var e = new Error('Can not set remote ' + description.type +
-            ' in state ' + self.signalingState);
-        e.name = 'InvalidStateError';
-        if (args.length > 2 && typeof args[2] === 'function') {
-          args[2].apply(null, [e]);
-        }
-        reject(e);
-      });
-    }
-
-    var streams = {};
-    this.remoteStreams.forEach(function(stream) {
-      streams[stream.id] = stream;
-    });
-    var receiverList = [];
-    var sections = SDPUtils.splitSections(description.sdp);
-    var sessionpart = sections.shift();
-    var isIceLite = SDPUtils.matchPrefix(sessionpart,
-        'a=ice-lite').length > 0;
-    var usingBundle = SDPUtils.matchPrefix(sessionpart,
-        'a=group:BUNDLE ').length > 0;
-    this.usingBundle = usingBundle;
-    var iceOptions = SDPUtils.matchPrefix(sessionpart,
-        'a=ice-options:')[0];
-    if (iceOptions) {
-      this.canTrickleIceCandidates = iceOptions.substr(14).split(' ')
-          .indexOf('trickle') >= 0;
-    } else {
-      this.canTrickleIceCandidates = false;
-    }
-
-    sections.forEach(function(mediaSection, sdpMLineIndex) {
-      var lines = SDPUtils.splitLines(mediaSection);
-      var kind = SDPUtils.getKind(mediaSection);
-      // treat bundle-only as not-rejected.
-      var rejected = SDPUtils.isRejected(mediaSection) &&
-          !SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 1;
-      var protocol = lines[0].substr(2).split(' ')[2];
-
-      var direction = SDPUtils.getDirection(mediaSection, sessionpart);
-      var remoteMsid = SDPUtils.parseMsid(mediaSection);
-
-      var mid = SDPUtils.getMid(mediaSection) || SDPUtils.generateIdentifier();
-
-      // Reject datachannels which are not implemented yet.
-      if (kind === 'application' && protocol === 'DTLS/SCTP') {
-        self.transceivers[sdpMLineIndex] = {
-          mid: mid,
-          isDatachannel: true
-        };
-        return;
-      }
-
-      var transceiver;
-      var iceGatherer;
-      var iceTransport;
-      var dtlsTransport;
-      var rtpReceiver;
-      var sendEncodingParameters;
-      var recvEncodingParameters;
-      var localCapabilities;
-
-      var track;
-      // FIXME: ensure the mediaSection has rtcp-mux set.
-      var remoteCapabilities = SDPUtils.parseRtpParameters(mediaSection);
-      var remoteIceParameters;
-      var remoteDtlsParameters;
-      if (!rejected) {
-        remoteIceParameters = SDPUtils.getIceParameters(mediaSection,
-            sessionpart);
-        remoteDtlsParameters = SDPUtils.getDtlsParameters(mediaSection,
-            sessionpart);
-        remoteDtlsParameters.role = 'client';
-      }
-      recvEncodingParameters =
-          SDPUtils.parseRtpEncodingParameters(mediaSection);
-
-      var rtcpParameters = SDPUtils.parseRtcpParameters(mediaSection);
-
-      var isComplete = SDPUtils.matchPrefix(mediaSection,
-          'a=end-of-candidates', sessionpart).length > 0;
-      var cands = SDPUtils.matchPrefix(mediaSection, 'a=candidate:')
-          .map(function(cand) {
-            return SDPUtils.parseCandidate(cand);
-          })
-          .filter(function(cand) {
-            return cand.component === 1;
-          });
-
-      // Check if we can use BUNDLE and dispose transports.
-      if ((description.type === 'offer' || description.type === 'answer') &&
-          !rejected && usingBundle && sdpMLineIndex > 0 &&
-          self.transceivers[sdpMLineIndex]) {
-        self._disposeIceAndDtlsTransports(sdpMLineIndex);
-        self.transceivers[sdpMLineIndex].iceGatherer =
-            self.transceivers[0].iceGatherer;
-        self.transceivers[sdpMLineIndex].iceTransport =
-            self.transceivers[0].iceTransport;
-        self.transceivers[sdpMLineIndex].dtlsTransport =
-            self.transceivers[0].dtlsTransport;
-        if (self.transceivers[sdpMLineIndex].rtpSender) {
-          self.transceivers[sdpMLineIndex].rtpSender.setTransport(
-              self.transceivers[0].dtlsTransport);
-        }
-        if (self.transceivers[sdpMLineIndex].rtpReceiver) {
-          self.transceivers[sdpMLineIndex].rtpReceiver.setTransport(
-              self.transceivers[0].dtlsTransport);
-        }
-      }
-      if (description.type === 'offer' && !rejected) {
-        transceiver = self.transceivers[sdpMLineIndex] ||
-            self._createTransceiver(kind);
-        transceiver.mid = mid;
-
-        if (!transceiver.iceGatherer) {
-          transceiver.iceGatherer = self._createIceGatherer(sdpMLineIndex,
-              usingBundle);
-        }
-
-        if (cands.length && transceiver.iceTransport.state === 'new') {
-          if (isComplete && (!usingBundle || sdpMLineIndex === 0)) {
-            transceiver.iceTransport.setRemoteCandidates(cands);
-          } else {
-            cands.forEach(function(candidate) {
-              maybeAddCandidate(transceiver.iceTransport, candidate);
-            });
-          }
-        }
-
-        localCapabilities = window.RTCRtpReceiver.getCapabilities(kind);
-
-        // filter RTX until additional stuff needed for RTX is implemented
-        // in adapter.js
-        if (edgeVersion < 15019) {
-          localCapabilities.codecs = localCapabilities.codecs.filter(
-              function(codec) {
-                return codec.name !== 'rtx';
-              });
-        }
-
-        sendEncodingParameters = transceiver.sendEncodingParameters || [{
-          ssrc: (2 * sdpMLineIndex + 2) * 1001
-        }];
-
-        var isNewTrack = false;
-        if (direction === 'sendrecv' || direction === 'sendonly') {
-          isNewTrack = !transceiver.rtpReceiver;
-          rtpReceiver = transceiver.rtpReceiver ||
-              new window.RTCRtpReceiver(transceiver.dtlsTransport, kind);
-
-          if (isNewTrack) {
-            var stream;
-            track = rtpReceiver.track;
-            // FIXME: does not work with Plan B.
-            if (remoteMsid) {
-              if (!streams[remoteMsid.stream]) {
-                streams[remoteMsid.stream] = new window.MediaStream();
-                Object.defineProperty(streams[remoteMsid.stream], 'id', {
-                  get: function() {
-                    return remoteMsid.stream;
-                  }
-                });
-              }
-              Object.defineProperty(track, 'id', {
-                get: function() {
-                  return remoteMsid.track;
-                }
-              });
-              stream = streams[remoteMsid.stream];
-            } else {
-              if (!streams.default) {
-                streams.default = new window.MediaStream();
-              }
-              stream = streams.default;
-            }
-            stream.addTrack(track);
-            receiverList.push([track, rtpReceiver, stream]);
-          }
-        }
-
-        transceiver.localCapabilities = localCapabilities;
-        transceiver.remoteCapabilities = remoteCapabilities;
-        transceiver.rtpReceiver = rtpReceiver;
-        transceiver.rtcpParameters = rtcpParameters;
-        transceiver.sendEncodingParameters = sendEncodingParameters;
-        transceiver.recvEncodingParameters = recvEncodingParameters;
-
-        // Start the RTCRtpReceiver now. The RTPSender is started in
-        // setLocalDescription.
-        self._transceive(self.transceivers[sdpMLineIndex],
-            false,
-            isNewTrack);
-      } else if (description.type === 'answer' && !rejected) {
-        transceiver = self.transceivers[sdpMLineIndex];
-        iceGatherer = transceiver.iceGatherer;
-        iceTransport = transceiver.iceTransport;
-        dtlsTransport = transceiver.dtlsTransport;
-        rtpReceiver = transceiver.rtpReceiver;
-        sendEncodingParameters = transceiver.sendEncodingParameters;
-        localCapabilities = transceiver.localCapabilities;
-
-        self.transceivers[sdpMLineIndex].recvEncodingParameters =
-            recvEncodingParameters;
-        self.transceivers[sdpMLineIndex].remoteCapabilities =
-            remoteCapabilities;
-        self.transceivers[sdpMLineIndex].rtcpParameters = rtcpParameters;
-
-        if (cands.length && iceTransport.state === 'new') {
-          if ((isIceLite || isComplete) &&
-              (!usingBundle || sdpMLineIndex === 0)) {
-            iceTransport.setRemoteCandidates(cands);
-          } else {
-            cands.forEach(function(candidate) {
-              maybeAddCandidate(transceiver.iceTransport, candidate);
-            });
-          }
-        }
-
-        if (!usingBundle || sdpMLineIndex === 0) {
-          if (iceTransport.state === 'new') {
-            iceTransport.start(iceGatherer, remoteIceParameters,
-                'controlling');
-          }
-          if (dtlsTransport.state === 'new') {
-            dtlsTransport.start(remoteDtlsParameters);
-          }
-        }
-
-        self._transceive(transceiver,
-            direction === 'sendrecv' || direction === 'recvonly',
-            direction === 'sendrecv' || direction === 'sendonly');
-
-        if (rtpReceiver &&
-            (direction === 'sendrecv' || direction === 'sendonly')) {
-          track = rtpReceiver.track;
-          if (remoteMsid) {
-            if (!streams[remoteMsid.stream]) {
-              streams[remoteMsid.stream] = new window.MediaStream();
-            }
-            streams[remoteMsid.stream].addTrack(track);
-            receiverList.push([track, rtpReceiver, streams[remoteMsid.stream]]);
-          } else {
-            if (!streams.default) {
-              streams.default = new window.MediaStream();
-            }
-            streams.default.addTrack(track);
-            receiverList.push([track, rtpReceiver, streams.default]);
-          }
-        } else {
-          // FIXME: actually the receiver should be created later.
-          delete transceiver.rtpReceiver;
-        }
-      }
-    });
-
-    if (this._dtlsRole === undefined) {
-      this._dtlsRole = description.type === 'offer' ? 'active' : 'passive';
-    }
-
-    this.remoteDescription = {
-      type: description.type,
-      sdp: description.sdp
-    };
-    switch (description.type) {
-      case 'offer':
-        this._updateSignalingState('have-remote-offer');
-        break;
-      case 'answer':
-        this._updateSignalingState('stable');
-        break;
-      default:
-        throw new TypeError('unsupported type "' + description.type +
-            '"');
-    }
-    Object.keys(streams).forEach(function(sid) {
-      var stream = streams[sid];
-      if (stream.getTracks().length) {
-        if (self.remoteStreams.indexOf(stream) === -1) {
-          self.remoteStreams.push(stream);
-          var event = new Event('addstream');
-          event.stream = stream;
-          window.setTimeout(function() {
-            self.dispatchEvent(event);
-            if (typeof self.onaddstream === 'function') {
-              self.onaddstream(event);
-            }
-          });
-        }
-
-        receiverList.forEach(function(item) {
-          var track = item[0];
-          var receiver = item[1];
-          if (stream.id !== item[2].id) {
-            return;
-          }
-          var trackEvent = new Event('track');
-          trackEvent.track = track;
-          trackEvent.receiver = receiver;
-          trackEvent.transceiver = {receiver: receiver};
-          trackEvent.streams = [stream];
-          window.setTimeout(function() {
-            self.dispatchEvent(trackEvent);
-            if (typeof self.ontrack === 'function') {
-              self.ontrack(trackEvent);
-            }
-          });
-        });
-      }
-    });
-
-    // check whether addIceCandidate({}) was called within four seconds after
-    // setRemoteDescription.
-    window.setTimeout(function() {
-      if (!(self && self.transceivers)) {
-        return;
-      }
-      self.transceivers.forEach(function(transceiver) {
-        if (transceiver.iceTransport &&
-            transceiver.iceTransport.state === 'new' &&
-            transceiver.iceTransport.getRemoteCandidates().length > 0) {
-          console.warn('Timeout for addRemoteCandidate. Consider sending ' +
-              'an end-of-candidates notification');
-          transceiver.iceTransport.addRemoteCandidate({});
-        }
-      });
-    }, 4000);
-
-    return new Promise(function(resolve) {
-      if (args.length > 1 && typeof args[1] === 'function') {
-        args[1].apply(null);
-      }
-      resolve();
-    });
-  };
-
-  RTCPeerConnection.prototype.close = function() {
-    this.transceivers.forEach(function(transceiver) {
-      /* not yet
-      if (transceiver.iceGatherer) {
-        transceiver.iceGatherer.close();
-      }
-      */
-      if (transceiver.iceTransport) {
-        transceiver.iceTransport.stop();
-      }
-      if (transceiver.dtlsTransport) {
-        transceiver.dtlsTransport.stop();
-      }
-      if (transceiver.rtpSender) {
-        transceiver.rtpSender.stop();
-      }
-      if (transceiver.rtpReceiver) {
-        transceiver.rtpReceiver.stop();
-      }
-    });
-    // FIXME: clean up tracks, local streams, remote streams, etc
-    this._updateSignalingState('closed');
-  };
-
-  // Update the signaling state.
-  RTCPeerConnection.prototype._updateSignalingState = function(newState) {
-    this.signalingState = newState;
-    var event = new Event('signalingstatechange');
-    this.dispatchEvent(event);
-    if (typeof this.onsignalingstatechange === 'function') {
-      this.onsignalingstatechange(event);
-    }
-  };
-
-  // Determine whether to fire the negotiationneeded event.
-  RTCPeerConnection.prototype._maybeFireNegotiationNeeded = function() {
-    var self = this;
-    if (this.signalingState !== 'stable' || this.needNegotiation === true) {
-      return;
-    }
-    this.needNegotiation = true;
-    window.setTimeout(function() {
-      if (self.needNegotiation === false) {
-        return;
-      }
-      self.needNegotiation = false;
-      var event = new Event('negotiationneeded');
-      self.dispatchEvent(event);
-      if (typeof self.onnegotiationneeded === 'function') {
-        self.onnegotiationneeded(event);
-      }
-    }, 0);
-  };
-
-  // Update the connection state.
-  RTCPeerConnection.prototype._updateConnectionState = function() {
-    var newState;
-    var states = {
-      'new': 0,
-      closed: 0,
-      connecting: 0,
-      checking: 0,
-      connected: 0,
-      completed: 0,
-      disconnected: 0,
-      failed: 0
-    };
-    this.transceivers.forEach(function(transceiver) {
-      states[transceiver.iceTransport.state]++;
-      states[transceiver.dtlsTransport.state]++;
-    });
-    // ICETransport.completed and connected are the same for this purpose.
-    states.connected += states.completed;
-
-    newState = 'new';
-    if (states.failed > 0) {
-      newState = 'failed';
-    } else if (states.connecting > 0 || states.checking > 0) {
-      newState = 'connecting';
-    } else if (states.disconnected > 0) {
-      newState = 'disconnected';
-    } else if (states.new > 0) {
-      newState = 'new';
-    } else if (states.connected > 0 || states.completed > 0) {
-      newState = 'connected';
-    }
-
-    if (newState !== this.iceConnectionState) {
-      this.iceConnectionState = newState;
-      var event = new Event('iceconnectionstatechange');
-      this.dispatchEvent(event);
-      if (typeof this.oniceconnectionstatechange === 'function') {
-        this.oniceconnectionstatechange(event);
-      }
-    }
-  };
-
-  RTCPeerConnection.prototype.createOffer = function() {
-    var self = this;
-    var args = arguments;
-
-    var offerOptions;
-    if (arguments.length === 1 && typeof arguments[0] !== 'function') {
-      offerOptions = arguments[0];
-    } else if (arguments.length === 3) {
-      offerOptions = arguments[2];
-    }
-
-    var numAudioTracks = this.transceivers.filter(function(t) {
-      return t.kind === 'audio';
-    }).length;
-    var numVideoTracks = this.transceivers.filter(function(t) {
-      return t.kind === 'video';
-    }).length;
-
-    // Determine number of audio and video tracks we need to send/recv.
-    if (offerOptions) {
-      // Reject Chrome legacy constraints.
-      if (offerOptions.mandatory || offerOptions.optional) {
-        throw new TypeError(
-            'Legacy mandatory/optional constraints not supported.');
-      }
-      if (offerOptions.offerToReceiveAudio !== undefined) {
-        if (offerOptions.offerToReceiveAudio === true) {
-          numAudioTracks = 1;
-        } else if (offerOptions.offerToReceiveAudio === false) {
-          numAudioTracks = 0;
-        } else {
-          numAudioTracks = offerOptions.offerToReceiveAudio;
-        }
-      }
-      if (offerOptions.offerToReceiveVideo !== undefined) {
-        if (offerOptions.offerToReceiveVideo === true) {
-          numVideoTracks = 1;
-        } else if (offerOptions.offerToReceiveVideo === false) {
-          numVideoTracks = 0;
-        } else {
-          numVideoTracks = offerOptions.offerToReceiveVideo;
-        }
-      }
-    }
-
-    this.transceivers.forEach(function(transceiver) {
-      if (transceiver.kind === 'audio') {
-        numAudioTracks--;
-        if (numAudioTracks < 0) {
-          transceiver.wantReceive = false;
-        }
-      } else if (transceiver.kind === 'video') {
-        numVideoTracks--;
-        if (numVideoTracks < 0) {
-          transceiver.wantReceive = false;
-        }
-      }
-    });
-
-    // Create M-lines for recvonly streams.
-    while (numAudioTracks > 0 || numVideoTracks > 0) {
-      if (numAudioTracks > 0) {
-        this._createTransceiver('audio');
-        numAudioTracks--;
-      }
-      if (numVideoTracks > 0) {
-        this._createTransceiver('video');
-        numVideoTracks--;
-      }
-    }
-
-    var sdp = SDPUtils.writeSessionBoilerplate(this._sdpSessionId,
-        this._sdpSessionVersion++);
-    this.transceivers.forEach(function(transceiver, sdpMLineIndex) {
-      // For each track, create an ice gatherer, ice transport,
-      // dtls transport, potentially rtpsender and rtpreceiver.
-      var track = transceiver.track;
-      var kind = transceiver.kind;
-      var mid = SDPUtils.generateIdentifier();
-      transceiver.mid = mid;
-
-      if (!transceiver.iceGatherer) {
-        transceiver.iceGatherer = self._createIceGatherer(sdpMLineIndex,
-            self.usingBundle);
-      }
-
-      var localCapabilities = window.RTCRtpSender.getCapabilities(kind);
-      // filter RTX until additional stuff needed for RTX is implemented
-      // in adapter.js
-      if (edgeVersion < 15019) {
-        localCapabilities.codecs = localCapabilities.codecs.filter(
-            function(codec) {
-              return codec.name !== 'rtx';
-            });
-      }
-      localCapabilities.codecs.forEach(function(codec) {
-        // work around https://bugs.chromium.org/p/webrtc/issues/detail?id=6552
-        // by adding level-asymmetry-allowed=1
-        if (codec.name === 'H264' &&
-            codec.parameters['level-asymmetry-allowed'] === undefined) {
-          codec.parameters['level-asymmetry-allowed'] = '1';
-        }
-      });
-
-      // generate an ssrc now, to be used later in rtpSender.send
-      var sendEncodingParameters = transceiver.sendEncodingParameters || [{
-        ssrc: (2 * sdpMLineIndex + 1) * 1001
-      }];
-      if (track) {
-        // add RTX
-        if (edgeVersion >= 15019 && kind === 'video' &&
-            !sendEncodingParameters[0].rtx) {
-          sendEncodingParameters[0].rtx = {
-            ssrc: sendEncodingParameters[0].ssrc + 1
-          };
-        }
-      }
-
-      if (transceiver.wantReceive) {
-        transceiver.rtpReceiver = new window.RTCRtpReceiver(
-            transceiver.dtlsTransport, kind);
-      }
-
-      transceiver.localCapabilities = localCapabilities;
-      transceiver.sendEncodingParameters = sendEncodingParameters;
-    });
-
-    // always offer BUNDLE and dispose on return if not supported.
-    if (this._config.bundlePolicy !== 'max-compat') {
-      sdp += 'a=group:BUNDLE ' + this.transceivers.map(function(t) {
-        return t.mid;
-      }).join(' ') + '\r\n';
-    }
-    sdp += 'a=ice-options:trickle\r\n';
-
-    this.transceivers.forEach(function(transceiver, sdpMLineIndex) {
-      sdp += writeMediaSection(transceiver, transceiver.localCapabilities,
-          'offer', transceiver.stream, self._dtlsRole);
-      sdp += 'a=rtcp-rsize\r\n';
-
-      if (transceiver.iceGatherer && self.iceGatheringState !== 'new' &&
-          (sdpMLineIndex === 0 || !self.usingBundle)) {
-        transceiver.iceGatherer.getLocalCandidates().forEach(function(cand) {
-          cand.component = 1;
-          sdp += 'a=' + SDPUtils.writeCandidate(cand) + '\r\n';
-        });
-
-        if (transceiver.iceGatherer.state === 'completed') {
-          sdp += 'a=end-of-candidates\r\n';
-        }
-      }
-    });
-
-    var desc = new window.RTCSessionDescription({
-      type: 'offer',
-      sdp: sdp
-    });
-    return new Promise(function(resolve) {
-      if (args.length > 0 && typeof args[0] === 'function') {
-        args[0].apply(null, [desc]);
-        resolve();
-        return;
-      }
-      resolve(desc);
-    });
-  };
-
-  RTCPeerConnection.prototype.createAnswer = function() {
-    var self = this;
-    var args = arguments;
-
-    var sdp = SDPUtils.writeSessionBoilerplate(this._sdpSessionId,
-        this._sdpSessionVersion++);
-    if (this.usingBundle) {
-      sdp += 'a=group:BUNDLE ' + this.transceivers.map(function(t) {
-        return t.mid;
-      }).join(' ') + '\r\n';
-    }
-    var mediaSectionsInOffer = SDPUtils.splitSections(
-        this.remoteDescription.sdp).length - 1;
-    this.transceivers.forEach(function(transceiver, sdpMLineIndex) {
-      if (sdpMLineIndex + 1 > mediaSectionsInOffer) {
-        return;
-      }
-      if (transceiver.isDatachannel) {
-        sdp += 'm=application 0 DTLS/SCTP 5000\r\n' +
-            'c=IN IP4 0.0.0.0\r\n' +
-            'a=mid:' + transceiver.mid + '\r\n';
-        return;
-      }
-
-      // FIXME: look at direction.
-      if (transceiver.stream) {
-        var localTrack;
-        if (transceiver.kind === 'audio') {
-          localTrack = transceiver.stream.getAudioTracks()[0];
-        } else if (transceiver.kind === 'video') {
-          localTrack = transceiver.stream.getVideoTracks()[0];
-        }
-        if (localTrack) {
-          // add RTX
-          if (edgeVersion >= 15019 && transceiver.kind === 'video' &&
-              !transceiver.sendEncodingParameters[0].rtx) {
-            transceiver.sendEncodingParameters[0].rtx = {
-              ssrc: transceiver.sendEncodingParameters[0].ssrc + 1
-            };
-          }
-        }
-      }
-
-      // Calculate intersection of capabilities.
-      var commonCapabilities = getCommonCapabilities(
-          transceiver.localCapabilities,
-          transceiver.remoteCapabilities);
-
-      var hasRtx = commonCapabilities.codecs.filter(function(c) {
-        return c.name.toLowerCase() === 'rtx';
-      }).length;
-      if (!hasRtx && transceiver.sendEncodingParameters[0].rtx) {
-        delete transceiver.sendEncodingParameters[0].rtx;
-      }
-
-      sdp += writeMediaSection(transceiver, commonCapabilities,
-          'answer', transceiver.stream, self._dtlsRole);
-      if (transceiver.rtcpParameters &&
-          transceiver.rtcpParameters.reducedSize) {
-        sdp += 'a=rtcp-rsize\r\n';
-      }
-    });
-
-    var desc = new window.RTCSessionDescription({
-      type: 'answer',
-      sdp: sdp
-    });
-    return new Promise(function(resolve) {
-      if (args.length > 0 && typeof args[0] === 'function') {
-        args[0].apply(null, [desc]);
-        resolve();
-        return;
-      }
-      resolve(desc);
-    });
-  };
-
-  RTCPeerConnection.prototype.addIceCandidate = function(candidate) {
-    var err;
-    var sections;
-    if (!candidate || candidate.candidate === '') {
-      for (var j = 0; j < this.transceivers.length; j++) {
-        if (this.transceivers[j].isDatachannel) {
-          continue;
-        }
-        this.transceivers[j].iceTransport.addRemoteCandidate({});
-        sections = SDPUtils.splitSections(this.remoteDescription.sdp);
-        sections[j + 1] += 'a=end-of-candidates\r\n';
-        this.remoteDescription.sdp = sections.join('');
-        if (this.usingBundle) {
-          break;
-        }
-      }
-    } else if (!(candidate.sdpMLineIndex !== undefined || candidate.sdpMid)) {
-      throw new TypeError('sdpMLineIndex or sdpMid required');
-    } else if (!this.remoteDescription) {
-      err = new Error('Can not add ICE candidate without ' +
-          'a remote description');
-      err.name = 'InvalidStateError';
-    } else {
-      var sdpMLineIndex = candidate.sdpMLineIndex;
-      if (candidate.sdpMid) {
-        for (var i = 0; i < this.transceivers.length; i++) {
-          if (this.transceivers[i].mid === candidate.sdpMid) {
-            sdpMLineIndex = i;
-            break;
-          }
-        }
-      }
-      var transceiver = this.transceivers[sdpMLineIndex];
-      if (transceiver) {
-        if (transceiver.isDatachannel) {
-          return Promise.resolve();
-        }
-        var cand = Object.keys(candidate.candidate).length > 0 ?
-            SDPUtils.parseCandidate(candidate.candidate) : {};
-        // Ignore Chrome's invalid candidates since Edge does not like them.
-        if (cand.protocol === 'tcp' && (cand.port === 0 || cand.port === 9)) {
-          return Promise.resolve();
-        }
-        // Ignore RTCP candidates, we assume RTCP-MUX.
-        if (cand.component && cand.component !== 1) {
-          return Promise.resolve();
-        }
-        // when using bundle, avoid adding candidates to the wrong
-        // ice transport. And avoid adding candidates added in the SDP.
-        if (sdpMLineIndex === 0 || (sdpMLineIndex > 0 &&
-            transceiver.iceTransport !== this.transceivers[0].iceTransport)) {
-          if (!maybeAddCandidate(transceiver.iceTransport, cand)) {
-            err = new Error('Can not add ICE candidate');
-            err.name = 'OperationError';
-          }
-        }
-
-        if (!err) {
-          // update the remoteDescription.
-          var candidateString = candidate.candidate.trim();
-          if (candidateString.indexOf('a=') === 0) {
-            candidateString = candidateString.substr(2);
-          }
-          sections = SDPUtils.splitSections(this.remoteDescription.sdp);
-          sections[sdpMLineIndex + 1] += 'a=' +
-              (cand.type ? candidateString : 'end-of-candidates')
-              + '\r\n';
-          this.remoteDescription.sdp = sections.join('');
-        }
-      } else {
-        err = new Error('Can not add ICE candidate');
-        err.name = 'OperationError';
-      }
-    }
-    var args = arguments;
-    return new Promise(function(resolve, reject) {
-      if (err) {
-        if (args.length > 2 && typeof args[2] === 'function') {
-          args[2].apply(null, [err]);
-        }
-        reject(err);
-      } else {
-        if (args.length > 1 && typeof args[1] === 'function') {
-          args[1].apply(null);
-        }
-        resolve();
-      }
-    });
-  };
-
-  RTCPeerConnection.prototype.getStats = function() {
-    var promises = [];
-    this.transceivers.forEach(function(transceiver) {
-      ['rtpSender', 'rtpReceiver', 'iceGatherer', 'iceTransport',
-          'dtlsTransport'].forEach(function(method) {
-            if (transceiver[method]) {
-              promises.push(transceiver[method].getStats());
-            }
-          });
-    });
-    var cb = arguments.length > 1 && typeof arguments[1] === 'function' &&
-        arguments[1];
-    var fixStatsType = function(stat) {
-      return {
-        inboundrtp: 'inbound-rtp',
-        outboundrtp: 'outbound-rtp',
-        candidatepair: 'candidate-pair',
-        localcandidate: 'local-candidate',
-        remotecandidate: 'remote-candidate'
-      }[stat.type] || stat.type;
-    };
-    return new Promise(function(resolve) {
-      // shim getStats with maplike support
-      var results = new Map();
-      Promise.all(promises).then(function(res) {
-        res.forEach(function(result) {
-          Object.keys(result).forEach(function(id) {
-            result[id].type = fixStatsType(result[id]);
-            results.set(id, result[id]);
-          });
-        });
-        if (cb) {
-          cb.apply(null, results);
-        }
-        resolve(results);
-      });
-    });
-  };
-  return RTCPeerConnection;
-};
-
-},{"sdp":2}],2:[function(require,module,exports){
- /* eslint-env node */
-'use strict';
-
-// SDP helpers.
-var SDPUtils = {};
-
-// Generate an alphanumeric identifier for cname or mids.
-// TODO: use UUIDs instead? https://gist.github.com/jed/982883
-SDPUtils.generateIdentifier = function() {
-  return Math.random().toString(36).substr(2, 10);
-};
-
-// The RTCP CNAME used by all peerconnections from the same JS.
-SDPUtils.localCName = SDPUtils.generateIdentifier();
-
-// Splits SDP into lines, dealing with both CRLF and LF.
-SDPUtils.splitLines = function(blob) {
-  return blob.trim().split('\n').map(function(line) {
-    return line.trim();
-  });
-};
-// Splits SDP into sessionpart and mediasections. Ensures CRLF.
-SDPUtils.splitSections = function(blob) {
-  var parts = blob.split('\nm=');
-  return parts.map(function(part, index) {
-    return (index > 0 ? 'm=' + part : part).trim() + '\r\n';
-  });
-};
-
-// Returns lines that start with a certain prefix.
-SDPUtils.matchPrefix = function(blob, prefix) {
-  return SDPUtils.splitLines(blob).filter(function(line) {
-    return line.indexOf(prefix) === 0;
-  });
-};
-
-// Parses an ICE candidate line. Sample input:
-// candidate:702786350 2 udp 41819902 8.8.8.8 60769 typ relay raddr 8.8.8.8
-// rport 55996"
-SDPUtils.parseCandidate = function(line) {
-  var parts;
-  // Parse both variants.
-  if (line.indexOf('a=candidate:') === 0) {
-    parts = line.substring(12).split(' ');
-  } else {
-    parts = line.substring(10).split(' ');
-  }
-
-  var candidate = {
-    foundation: parts[0],
-    component: parseInt(parts[1], 10),
-    protocol: parts[2].toLowerCase(),
-    priority: parseInt(parts[3], 10),
-    ip: parts[4],
-    port: parseInt(parts[5], 10),
-    // skip parts[6] == 'typ'
-    type: parts[7]
-  };
-
-  for (var i = 8; i < parts.length; i += 2) {
-    switch (parts[i]) {
-      case 'raddr':
-        candidate.relatedAddress = parts[i + 1];
-        break;
-      case 'rport':
-        candidate.relatedPort = parseInt(parts[i + 1], 10);
-        break;
-      case 'tcptype':
-        candidate.tcpType = parts[i + 1];
-        break;
-      case 'ufrag':
-        candidate.ufrag = parts[i + 1]; // for backward compability.
-        candidate.usernameFragment = parts[i + 1];
-        break;
-      default: // extension handling, in particular ufrag
-        candidate[parts[i]] = parts[i + 1];
-        break;
-    }
-  }
-  return candidate;
-};
-
-// Translates a candidate object into SDP candidate attribute.
-SDPUtils.writeCandidate = function(candidate) {
-  var sdp = [];
-  sdp.push(candidate.foundation);
-  sdp.push(candidate.component);
-  sdp.push(candidate.protocol.toUpperCase());
-  sdp.push(candidate.priority);
-  sdp.push(candidate.ip);
-  sdp.push(candidate.port);
-
-  var type = candidate.type;
-  sdp.push('typ');
-  sdp.push(type);
-  if (type !== 'host' && candidate.relatedAddress &&
-      candidate.relatedPort) {
-    sdp.push('raddr');
-    sdp.push(candidate.relatedAddress); // was: relAddr
-    sdp.push('rport');
-    sdp.push(candidate.relatedPort); // was: relPort
-  }
-  if (candidate.tcpType && candidate.protocol.toLowerCase() === 'tcp') {
-    sdp.push('tcptype');
-    sdp.push(candidate.tcpType);
-  }
-  if (candidate.ufrag) {
-    sdp.push('ufrag');
-    sdp.push(candidate.ufrag);
-  }
-  return 'candidate:' + sdp.join(' ');
-};
-
-// Parses an ice-options line, returns an array of option tags.
-// a=ice-options:foo bar
-SDPUtils.parseIceOptions = function(line) {
-  return line.substr(14).split(' ');
-}
-
-// Parses an rtpmap line, returns RTCRtpCoddecParameters. Sample input:
-// a=rtpmap:111 opus/48000/2
-SDPUtils.parseRtpMap = function(line) {
-  var parts = line.substr(9).split(' ');
-  var parsed = {
-    payloadType: parseInt(parts.shift(), 10) // was: id
-  };
-
-  parts = parts[0].split('/');
-
-  parsed.name = parts[0];
-  parsed.clockRate = parseInt(parts[1], 10); // was: clockrate
-  // was: channels
-  parsed.numChannels = parts.length === 3 ? parseInt(parts[2], 10) : 1;
-  return parsed;
-};
-
-// Generate an a=rtpmap line from RTCRtpCodecCapability or
-// RTCRtpCodecParameters.
-SDPUtils.writeRtpMap = function(codec) {
-  var pt = codec.payloadType;
-  if (codec.preferredPayloadType !== undefined) {
-    pt = codec.preferredPayloadType;
-  }
-  return 'a=rtpmap:' + pt + ' ' + codec.name + '/' + codec.clockRate +
-      (codec.numChannels !== 1 ? '/' + codec.numChannels : '') + '\r\n';
-};
-
-// Parses an a=extmap line (headerextension from RFC 5285). Sample input:
-// a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
-// a=extmap:2/sendonly urn:ietf:params:rtp-hdrext:toffset
-SDPUtils.parseExtmap = function(line) {
-  var parts = line.substr(9).split(' ');
-  return {
-    id: parseInt(parts[0], 10),
-    direction: parts[0].indexOf('/') > 0 ? parts[0].split('/')[1] : 'sendrecv',
-    uri: parts[1]
-  };
-};
-
-// Generates a=extmap line from RTCRtpHeaderExtensionParameters or
-// RTCRtpHeaderExtension.
-SDPUtils.writeExtmap = function(headerExtension) {
-  return 'a=extmap:' + (headerExtension.id || headerExtension.preferredId) +
-      (headerExtension.direction && headerExtension.direction !== 'sendrecv'
-          ? '/' + headerExtension.direction
-          : '') +
-      ' ' + headerExtension.uri + '\r\n';
-};
-
-// Parses an ftmp line, returns dictionary. Sample input:
-// a=fmtp:96 vbr=on;cng=on
-// Also deals with vbr=on; cng=on
-SDPUtils.parseFmtp = function(line) {
-  var parsed = {};
-  var kv;
-  var parts = line.substr(line.indexOf(' ') + 1).split(';');
-  for (var j = 0; j < parts.length; j++) {
-    kv = parts[j].trim().split('=');
-    parsed[kv[0].trim()] = kv[1];
-  }
-  return parsed;
-};
-
-// Generates an a=ftmp line from RTCRtpCodecCapability or RTCRtpCodecParameters.
-SDPUtils.writeFmtp = function(codec) {
-  var line = '';
-  var pt = codec.payloadType;
-  if (codec.preferredPayloadType !== undefined) {
-    pt = codec.preferredPayloadType;
-  }
-  if (codec.parameters && Object.keys(codec.parameters).length) {
-    var params = [];
-    Object.keys(codec.parameters).forEach(function(param) {
-      params.push(param + '=' + codec.parameters[param]);
-    });
-    line += 'a=fmtp:' + pt + ' ' + params.join(';') + '\r\n';
-  }
-  return line;
-};
-
-// Parses an rtcp-fb line, returns RTCPRtcpFeedback object. Sample input:
-// a=rtcp-fb:98 nack rpsi
-SDPUtils.parseRtcpFb = function(line) {
-  var parts = line.substr(line.indexOf(' ') + 1).split(' ');
-  return {
-    type: parts.shift(),
-    parameter: parts.join(' ')
-  };
-};
-// Generate a=rtcp-fb lines from RTCRtpCodecCapability or RTCRtpCodecParameters.
-SDPUtils.writeRtcpFb = function(codec) {
-  var lines = '';
-  var pt = codec.payloadType;
-  if (codec.preferredPayloadType !== undefined) {
-    pt = codec.preferredPayloadType;
-  }
-  if (codec.rtcpFeedback && codec.rtcpFeedback.length) {
-    // FIXME: special handling for trr-int?
-    codec.rtcpFeedback.forEach(function(fb) {
-      lines += 'a=rtcp-fb:' + pt + ' ' + fb.type +
-      (fb.parameter && fb.parameter.length ? ' ' + fb.parameter : '') +
-          '\r\n';
-    });
-  }
-  return lines;
-};
-
-// Parses an RFC 5576 ssrc media attribute. Sample input:
-// a=ssrc:3735928559 cname:something
-SDPUtils.parseSsrcMedia = function(line) {
-  var sp = line.indexOf(' ');
-  var parts = {
-    ssrc: parseInt(line.substr(7, sp - 7), 10)
-  };
-  var colon = line.indexOf(':', sp);
-  if (colon > -1) {
-    parts.attribute = line.substr(sp + 1, colon - sp - 1);
-    parts.value = line.substr(colon + 1);
-  } else {
-    parts.attribute = line.substr(sp + 1);
-  }
-  return parts;
-};
-
-// Extracts the MID (RFC 5888) from a media section.
-// returns the MID or undefined if no mid line was found.
-SDPUtils.getMid = function(mediaSection) {
-  var mid = SDPUtils.matchPrefix(mediaSection, 'a=mid:')[0];
-  if (mid) {
-    return mid.substr(6);
-  }
-}
-
-SDPUtils.parseFingerprint = function(line) {
-  var parts = line.substr(14).split(' ');
-  return {
-    algorithm: parts[0].toLowerCase(), // algorithm is case-sensitive in Edge.
-    value: parts[1]
-  };
-};
-
-// Extracts DTLS parameters from SDP media section or sessionpart.
-// FIXME: for consistency with other functions this should only
-//   get the fingerprint line as input. See also getIceParameters.
-SDPUtils.getDtlsParameters = function(mediaSection, sessionpart) {
-  var lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
-      'a=fingerprint:');
-  // Note: a=setup line is ignored since we use the 'auto' role.
-  // Note2: 'algorithm' is not case sensitive except in Edge.
-  return {
-    role: 'auto',
-    fingerprints: lines.map(SDPUtils.parseFingerprint)
-  };
-};
-
-// Serializes DTLS parameters to SDP.
-SDPUtils.writeDtlsParameters = function(params, setupType) {
-  var sdp = 'a=setup:' + setupType + '\r\n';
-  params.fingerprints.forEach(function(fp) {
-    sdp += 'a=fingerprint:' + fp.algorithm + ' ' + fp.value + '\r\n';
-  });
-  return sdp;
-};
-// Parses ICE information from SDP media section or sessionpart.
-// FIXME: for consistency with other functions this should only
-//   get the ice-ufrag and ice-pwd lines as input.
-SDPUtils.getIceParameters = function(mediaSection, sessionpart) {
-  var lines = SDPUtils.splitLines(mediaSection);
-  // Search in session part, too.
-  lines = lines.concat(SDPUtils.splitLines(sessionpart));
-  var iceParameters = {
-    usernameFragment: lines.filter(function(line) {
-      return line.indexOf('a=ice-ufrag:') === 0;
-    })[0].substr(12),
-    password: lines.filter(function(line) {
-      return line.indexOf('a=ice-pwd:') === 0;
-    })[0].substr(10)
-  };
-  return iceParameters;
-};
-
-// Serializes ICE parameters to SDP.
-SDPUtils.writeIceParameters = function(params) {
-  return 'a=ice-ufrag:' + params.usernameFragment + '\r\n' +
-      'a=ice-pwd:' + params.password + '\r\n';
-};
-
-// Parses the SDP media section and returns RTCRtpParameters.
-SDPUtils.parseRtpParameters = function(mediaSection) {
-  var description = {
-    codecs: [],
-    headerExtensions: [],
-    fecMechanisms: [],
-    rtcp: []
-  };
-  var lines = SDPUtils.splitLines(mediaSection);
-  var mline = lines[0].split(' ');
-  for (var i = 3; i < mline.length; i++) { // find all codecs from mline[3..]
-    var pt = mline[i];
-    var rtpmapline = SDPUtils.matchPrefix(
-        mediaSection, 'a=rtpmap:' + pt + ' ')[0];
-    if (rtpmapline) {
-      var codec = SDPUtils.parseRtpMap(rtpmapline);
-      var fmtps = SDPUtils.matchPrefix(
-          mediaSection, 'a=fmtp:' + pt + ' ');
-      // Only the first a=fmtp:<pt> is considered.
-      codec.parameters = fmtps.length ? SDPUtils.parseFmtp(fmtps[0]) : {};
-      codec.rtcpFeedback = SDPUtils.matchPrefix(
-          mediaSection, 'a=rtcp-fb:' + pt + ' ')
-        .map(SDPUtils.parseRtcpFb);
-      description.codecs.push(codec);
-      // parse FEC mechanisms from rtpmap lines.
-      switch (codec.name.toUpperCase()) {
-        case 'RED':
-        case 'ULPFEC':
-          description.fecMechanisms.push(codec.name.toUpperCase());
-          break;
-        default: // only RED and ULPFEC are recognized as FEC mechanisms.
-          break;
-      }
-    }
-  }
-  SDPUtils.matchPrefix(mediaSection, 'a=extmap:').forEach(function(line) {
-    description.headerExtensions.push(SDPUtils.parseExtmap(line));
-  });
-  // FIXME: parse rtcp.
-  return description;
-};
-
-// Generates parts of the SDP media section describing the capabilities /
-// parameters.
-SDPUtils.writeRtpDescription = function(kind, caps) {
-  var sdp = '';
-
-  // Build the mline.
-  sdp += 'm=' + kind + ' ';
-  sdp += caps.codecs.length > 0 ? '9' : '0'; // reject if no codecs.
-  sdp += ' UDP/TLS/RTP/SAVPF ';
-  sdp += caps.codecs.map(function(codec) {
-    if (codec.preferredPayloadType !== undefined) {
-      return codec.preferredPayloadType;
-    }
-    return codec.payloadType;
-  }).join(' ') + '\r\n';
-
-  sdp += 'c=IN IP4 0.0.0.0\r\n';
-  sdp += 'a=rtcp:9 IN IP4 0.0.0.0\r\n';
-
-  // Add a=rtpmap lines for each codec. Also fmtp and rtcp-fb.
-  caps.codecs.forEach(function(codec) {
-    sdp += SDPUtils.writeRtpMap(codec);
-    sdp += SDPUtils.writeFmtp(codec);
-    sdp += SDPUtils.writeRtcpFb(codec);
-  });
-  var maxptime = 0;
-  caps.codecs.forEach(function(codec) {
-    if (codec.maxptime > maxptime) {
-      maxptime = codec.maxptime;
-    }
-  });
-  if (maxptime > 0) {
-    sdp += 'a=maxptime:' + maxptime + '\r\n';
-  }
-  sdp += 'a=rtcp-mux\r\n';
-
-  caps.headerExtensions.forEach(function(extension) {
-    sdp += SDPUtils.writeExtmap(extension);
-  });
-  // FIXME: write fecMechanisms.
-  return sdp;
-};
-
-// Parses the SDP media section and returns an array of
-// RTCRtpEncodingParameters.
-SDPUtils.parseRtpEncodingParameters = function(mediaSection) {
-  var encodingParameters = [];
-  var description = SDPUtils.parseRtpParameters(mediaSection);
-  var hasRed = description.fecMechanisms.indexOf('RED') !== -1;
-  var hasUlpfec = description.fecMechanisms.indexOf('ULPFEC') !== -1;
-
-  // filter a=ssrc:... cname:, ignore PlanB-msid
-  var ssrcs = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
-  .map(function(line) {
-    return SDPUtils.parseSsrcMedia(line);
-  })
-  .filter(function(parts) {
-    return parts.attribute === 'cname';
-  });
-  var primarySsrc = ssrcs.length > 0 && ssrcs[0].ssrc;
-  var secondarySsrc;
-
-  var flows = SDPUtils.matchPrefix(mediaSection, 'a=ssrc-group:FID')
-  .map(function(line) {
-    var parts = line.split(' ');
-    parts.shift();
-    return parts.map(function(part) {
-      return parseInt(part, 10);
-    });
-  });
-  if (flows.length > 0 && flows[0].length > 1 && flows[0][0] === primarySsrc) {
-    secondarySsrc = flows[0][1];
-  }
-
-  description.codecs.forEach(function(codec) {
-    if (codec.name.toUpperCase() === 'RTX' && codec.parameters.apt) {
-      var encParam = {
-        ssrc: primarySsrc,
-        codecPayloadType: parseInt(codec.parameters.apt, 10),
-        rtx: {
-          ssrc: secondarySsrc
-        }
-      };
-      encodingParameters.push(encParam);
-      if (hasRed) {
-        encParam = JSON.parse(JSON.stringify(encParam));
-        encParam.fec = {
-          ssrc: secondarySsrc,
-          mechanism: hasUlpfec ? 'red+ulpfec' : 'red'
-        };
-        encodingParameters.push(encParam);
-      }
-    }
-  });
-  if (encodingParameters.length === 0 && primarySsrc) {
-    encodingParameters.push({
-      ssrc: primarySsrc
-    });
-  }
-
-  // we support both b=AS and b=TIAS but interpret AS as TIAS.
-  var bandwidth = SDPUtils.matchPrefix(mediaSection, 'b=');
-  if (bandwidth.length) {
-    if (bandwidth[0].indexOf('b=TIAS:') === 0) {
-      bandwidth = parseInt(bandwidth[0].substr(7), 10);
-    } else if (bandwidth[0].indexOf('b=AS:') === 0) {
-      // use formula from JSEP to convert b=AS to TIAS value.
-      bandwidth = parseInt(bandwidth[0].substr(5), 10) * 1000 * 0.95
-          - (50 * 40 * 8);
-    } else {
-      bandwidth = undefined;
-    }
-    encodingParameters.forEach(function(params) {
-      params.maxBitrate = bandwidth;
-    });
-  }
-  return encodingParameters;
-};
-
-// parses http://draft.ortc.org/#rtcrtcpparameters*
-SDPUtils.parseRtcpParameters = function(mediaSection) {
-  var rtcpParameters = {};
-
-  var cname;
-  // Gets the first SSRC. Note that with RTX there might be multiple
-  // SSRCs.
-  var remoteSsrc = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
-      .map(function(line) {
-        return SDPUtils.parseSsrcMedia(line);
-      })
-      .filter(function(obj) {
-        return obj.attribute === 'cname';
-      })[0];
-  if (remoteSsrc) {
-    rtcpParameters.cname = remoteSsrc.value;
-    rtcpParameters.ssrc = remoteSsrc.ssrc;
-  }
-
-  // Edge uses the compound attribute instead of reducedSize
-  // compound is !reducedSize
-  var rsize = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-rsize');
-  rtcpParameters.reducedSize = rsize.length > 0;
-  rtcpParameters.compound = rsize.length === 0;
-
-  // parses the rtcp-mux attrіbute.
-  // Note that Edge does not support unmuxed RTCP.
-  var mux = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-mux');
-  rtcpParameters.mux = mux.length > 0;
-
-  return rtcpParameters;
-};
-
-// parses either a=msid: or a=ssrc:... msid lines and returns
-// the id of the MediaStream and MediaStreamTrack.
-SDPUtils.parseMsid = function(mediaSection) {
-  var parts;
-  var spec = SDPUtils.matchPrefix(mediaSection, 'a=msid:');
-  if (spec.length === 1) {
-    parts = spec[0].substr(7).split(' ');
-    return {stream: parts[0], track: parts[1]};
-  }
-  var planB = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
-  .map(function(line) {
-    return SDPUtils.parseSsrcMedia(line);
-  })
-  .filter(function(parts) {
-    return parts.attribute === 'msid';
-  });
-  if (planB.length > 0) {
-    parts = planB[0].value.split(' ');
-    return {stream: parts[0], track: parts[1]};
-  }
-};
-
-// Generate a session ID for SDP.
-// https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-20#section-5.2.1
-// recommends using a cryptographically random +ve 64-bit value
-// but right now this should be acceptable and within the right range
-SDPUtils.generateSessionId = function() {
-  return Math.random().toString().substr(2, 21);
-};
-
-// Write boilder plate for start of SDP
-// sessId argument is optional - if not supplied it will
-// be generated randomly
-// sessVersion is optional and defaults to 2
-SDPUtils.writeSessionBoilerplate = function(sessId, sessVer) {
-  var sessionId;
-  var version = sessVer !== undefined ? sessVer : 2;
-  if (sessId) {
-    sessionId = sessId;
-  } else {
-    sessionId = SDPUtils.generateSessionId();
-  }
-  // FIXME: sess-id should be an NTP timestamp.
-  return 'v=0\r\n' +
-      'o=thisisadapterortc ' + sessionId + ' ' + version + ' IN IP4 127.0.0.1\r\n' +
-      's=-\r\n' +
-      't=0 0\r\n';
-};
-
-SDPUtils.writeMediaSection = function(transceiver, caps, type, stream) {
-  var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);
-
-  // Map ICE parameters (ufrag, pwd) to SDP.
-  sdp += SDPUtils.writeIceParameters(
-      transceiver.iceGatherer.getLocalParameters());
-
-  // Map DTLS parameters to SDP.
-  sdp += SDPUtils.writeDtlsParameters(
-      transceiver.dtlsTransport.getLocalParameters(),
-      type === 'offer' ? 'actpass' : 'active');
-
-  sdp += 'a=mid:' + transceiver.mid + '\r\n';
-
-  if (transceiver.direction) {
-    sdp += 'a=' + transceiver.direction + '\r\n';
-  } else if (transceiver.rtpSender && transceiver.rtpReceiver) {
-    sdp += 'a=sendrecv\r\n';
-  } else if (transceiver.rtpSender) {
-    sdp += 'a=sendonly\r\n';
-  } else if (transceiver.rtpReceiver) {
-    sdp += 'a=recvonly\r\n';
-  } else {
-    sdp += 'a=inactive\r\n';
-  }
-
-  if (transceiver.rtpSender) {
-    // spec.
-    var msid = 'msid:' + stream.id + ' ' +
-        transceiver.rtpSender.track.id + '\r\n';
-    sdp += 'a=' + msid;
-
-    // for Chrome.
-    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
-        ' ' + msid;
-    if (transceiver.sendEncodingParameters[0].rtx) {
-      sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
-          ' ' + msid;
-      sdp += 'a=ssrc-group:FID ' +
-          transceiver.sendEncodingParameters[0].ssrc + ' ' +
-          transceiver.sendEncodingParameters[0].rtx.ssrc +
-          '\r\n';
-    }
-  }
-  // FIXME: this should be written by writeRtpDescription.
-  sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
-      ' cname:' + SDPUtils.localCName + '\r\n';
-  if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
-    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
-        ' cname:' + SDPUtils.localCName + '\r\n';
-  }
-  return sdp;
-};
-
-// Gets the direction from the mediaSection or the sessionpart.
-SDPUtils.getDirection = function(mediaSection, sessionpart) {
-  // Look for sendrecv, sendonly, recvonly, inactive, default to sendrecv.
-  var lines = SDPUtils.splitLines(mediaSection);
-  for (var i = 0; i < lines.length; i++) {
-    switch (lines[i]) {
-      case 'a=sendrecv':
-      case 'a=sendonly':
-      case 'a=recvonly':
-      case 'a=inactive':
-        return lines[i].substr(2);
-      default:
-        // FIXME: What should happen here?
-    }
-  }
-  if (sessionpart) {
-    return SDPUtils.getDirection(sessionpart);
-  }
-  return 'sendrecv';
-};
-
-SDPUtils.getKind = function(mediaSection) {
-  var lines = SDPUtils.splitLines(mediaSection);
-  var mline = lines[0].split(' ');
-  return mline[0].substr(2);
-};
-
-SDPUtils.isRejected = function(mediaSection) {
-  return mediaSection.split(' ', 2)[1] === '0';
-};
-
-SDPUtils.parseMLine = function(mediaSection) {
-  var lines = SDPUtils.splitLines(mediaSection);
-  var mline = lines[0].split(' ');
-  return {
-    kind: mline[0].substr(2),
-    port: parseInt(mline[1], 10),
-    protocol: mline[2],
-    fmt: mline.slice(3).join(' ')
-  };
-};
-
-// Expose public methods.
-if (typeof module === 'object') {
-  module.exports = SDPUtils;
-}
-
-},{}],3:[function(require,module,exports){
-(function (global){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-
-'use strict';
-
-var adapterFactory = require('./adapter_factory.js');
-module.exports = adapterFactory({window: global.window});
-
-}).call(this,typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
-},{"./adapter_factory.js":4}],4:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-
-'use strict';
-
-var utils = require('./utils');
-// Shimming starts here.
-module.exports = function(dependencies, opts) {
-  var window = dependencies && dependencies.window;
-
-  var options = {
-    shimChrome: true,
-    shimFirefox: true,
-    shimEdge: true,
-    shimSafari: true,
-  };
-
-  for (var key in opts) {
-    if (hasOwnProperty.call(opts, key)) {
-      options[key] = opts[key];
-    }
-  }
-
-  // Utils.
-  var logging = utils.log;
-  var browserDetails = utils.detectBrowser(window);
-
-  // Export to the adapter global object visible in the browser.
-  var adapter = {
-    browserDetails: browserDetails,
-    extractVersion: utils.extractVersion,
-    disableLog: utils.disableLog,
-    disableWarnings: utils.disableWarnings
-  };
-
-  // Uncomment the line below if you want logging to occur, including logging
-  // for the switch statement below. Can also be turned on in the browser via
-  // adapter.disableLog(false), but then logging from the switch statement below
-  // will not appear.
-  // require('./utils').disableLog(false);
-
-  // Browser shims.
-  var chromeShim = require('./chrome/chrome_shim') || null;
-  var edgeShim = require('./edge/edge_shim') || null;
-  var firefoxShim = require('./firefox/firefox_shim') || null;
-  var safariShim = require('./safari/safari_shim') || null;
-  var commonShim = require('./common_shim') || null;
-
-  // Shim browser if found.
-  switch (browserDetails.browser) {
-    case 'chrome':
-      if (!chromeShim || !chromeShim.shimPeerConnection ||
-          !options.shimChrome) {
-        logging('Chrome shim is not included in this adapter release.');
-        return adapter;
-      }
-      logging('adapter.js shimming chrome.');
-      // Export to the adapter global object visible in the browser.
-      adapter.browserShim = chromeShim;
-      commonShim.shimCreateObjectURL(window);
-
-      chromeShim.shimGetUserMedia(window);
-      chromeShim.shimMediaStream(window);
-      chromeShim.shimSourceObject(window);
-      chromeShim.shimPeerConnection(window);
-      chromeShim.shimOnTrack(window);
-      chromeShim.shimAddTrackRemoveTrack(window);
-      chromeShim.shimGetSendersWithDtmf(window);
-
-      commonShim.shimRTCIceCandidate(window);
-      break;
-    case 'firefox':
-      if (!firefoxShim || !firefoxShim.shimPeerConnection ||
-          !options.shimFirefox) {
-        logging('Firefox shim is not included in this adapter release.');
-        return adapter;
-      }
-      logging('adapter.js shimming firefox.');
-      // Export to the adapter global object visible in the browser.
-      adapter.browserShim = firefoxShim;
-      commonShim.shimCreateObjectURL(window);
-
-      firefoxShim.shimGetUserMedia(window);
-      firefoxShim.shimSourceObject(window);
-      firefoxShim.shimPeerConnection(window);
-      firefoxShim.shimOnTrack(window);
-      firefoxShim.shimRemoveStream(window);
-
-      commonShim.shimRTCIceCandidate(window);
-      break;
-    case 'edge':
-      if (!edgeShim || !edgeShim.shimPeerConnection || !options.shimEdge) {
-        logging('MS edge shim is not included in this adapter release.');
-        return adapter;
-      }
-      logging('adapter.js shimming edge.');
-      // Export to the adapter global object visible in the browser.
-      adapter.browserShim = edgeShim;
-      commonShim.shimCreateObjectURL(window);
-
-      edgeShim.shimGetUserMedia(window);
-      edgeShim.shimPeerConnection(window);
-      edgeShim.shimReplaceTrack(window);
-
-      // the edge shim implements the full RTCIceCandidate object.
-      break;
-    case 'safari':
-      if (!safariShim || !options.shimSafari) {
-        logging('Safari shim is not included in this adapter release.');
-        return adapter;
-      }
-      logging('adapter.js shimming safari.');
-      // Export to the adapter global object visible in the browser.
-      adapter.browserShim = safariShim;
-      commonShim.shimCreateObjectURL(window);
-
-      safariShim.shimRTCIceServerUrls(window);
-      safariShim.shimCallbacksAPI(window);
-      safariShim.shimLocalStreamsAPI(window);
-      safariShim.shimRemoteStreamsAPI(window);
-      safariShim.shimTrackEventTransceiver(window);
-      safariShim.shimGetUserMedia(window);
-      safariShim.shimCreateOfferLegacy(window);
-
-      commonShim.shimRTCIceCandidate(window);
-      break;
-    default:
-      logging('Unsupported browser!');
-      break;
-  }
-
-  return adapter;
-};
-
-},{"./chrome/chrome_shim":5,"./common_shim":7,"./edge/edge_shim":8,"./firefox/firefox_shim":10,"./safari/safari_shim":12,"./utils":13}],5:[function(require,module,exports){
-
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
-var utils = require('../utils.js');
-var logging = utils.log;
-
-var chromeShim = {
-  shimMediaStream: function(window) {
-    window.MediaStream = window.MediaStream || window.webkitMediaStream;
-  },
-
-  shimOnTrack: function(window) {
-    if (typeof window === 'object' && window.RTCPeerConnection && !('ontrack' in
-        window.RTCPeerConnection.prototype)) {
-      Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
-        get: function() {
-          return this._ontrack;
-        },
-        set: function(f) {
-          if (this._ontrack) {
-            this.removeEventListener('track', this._ontrack);
-          }
-          this.addEventListener('track', this._ontrack = f);
-        }
-      });
-      var origSetRemoteDescription =
-          window.RTCPeerConnection.prototype.setRemoteDescription;
-      window.RTCPeerConnection.prototype.setRemoteDescription = function() {
-        var pc = this;
-        if (!pc._ontrackpoly) {
-          pc._ontrackpoly = function(e) {
-            // onaddstream does not fire when a track is added to an existing
-            // stream. But stream.onaddtrack is implemented so we use that.
-            e.stream.addEventListener('addtrack', function(te) {
-              var receiver;
-              if (window.RTCPeerConnection.prototype.getReceivers) {
-                receiver = pc.getReceivers().find(function(r) {
-                  return r.track && r.track.id === te.track.id;
-                });
-              } else {
-                receiver = {track: te.track};
-              }
-
-              var event = new Event('track');
-              event.track = te.track;
-              event.receiver = receiver;
-              event.transceiver = {receiver: receiver};
-              event.streams = [e.stream];
-              pc.dispatchEvent(event);
-            });
-            e.stream.getTracks().forEach(function(track) {
-              var receiver;
-              if (window.RTCPeerConnection.prototype.getReceivers) {
-                receiver = pc.getReceivers().find(function(r) {
-                  return r.track && r.track.id === track.id;
-                });
-              } else {
-                receiver = {track: track};
-              }
-              var event = new Event('track');
-              event.track = track;
-              event.receiver = receiver;
-              event.transceiver = {receiver: receiver};
-              event.streams = [e.stream];
-              pc.dispatchEvent(event);
-            });
-          };
-          pc.addEventListener('addstream', pc._ontrackpoly);
-        }
-        return origSetRemoteDescription.apply(pc, arguments);
-      };
-    }
-  },
-
-  shimGetSendersWithDtmf: function(window) {
-    // Overrides addTrack/removeTrack, depends on shimAddTrackRemoveTrack.
-    if (typeof window === 'object' && window.RTCPeerConnection &&
-        !('getSenders' in window.RTCPeerConnection.prototype) &&
-        'createDTMFSender' in window.RTCPeerConnection.prototype) {
-      var shimSenderWithDtmf = function(pc, track) {
-        return {
-          track: track,
-          get dtmf() {
-            if (this._dtmf === undefined) {
-              if (track.kind === 'audio') {
-                this._dtmf = pc.createDTMFSender(track);
-              } else {
-                this._dtmf = null;
-              }
-            }
-            return this._dtmf;
-          },
-          _pc: pc
-        };
-      };
-
-      // augment addTrack when getSenders is not available.
-      if (!window.RTCPeerConnection.prototype.getSenders) {
-        window.RTCPeerConnection.prototype.getSenders = function() {
-          this._senders = this._senders || [];
-          return this._senders.slice(); // return a copy of the internal state.
-        };
-        var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
-        window.RTCPeerConnection.prototype.addTrack = function(track, stream) {
-          var pc = this;
-          var sender = origAddTrack.apply(pc, arguments);
-          if (!sender) {
-            sender = shimSenderWithDtmf(pc, track);
-            pc._senders.push(sender);
-          }
-          return sender;
-        };
-
-        var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack;
-        window.RTCPeerConnection.prototype.removeTrack = function(sender) {
-          var pc = this;
-          origRemoveTrack.apply(pc, arguments);
-          var idx = pc._senders.indexOf(sender);
-          if (idx !== -1) {
-            pc._senders.splice(idx, 1);
-          }
-        };
-      }
-      var origAddStream = window.RTCPeerConnection.prototype.addStream;
-      window.RTCPeerConnection.prototype.addStream = function(stream) {
-        var pc = this;
-        pc._senders = pc._senders || [];
-        origAddStream.apply(pc, [stream]);
-        stream.getTracks().forEach(function(track) {
-          pc._senders.push(shimSenderWithDtmf(pc, track));
-        });
-      };
-
-      var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
-      window.RTCPeerConnection.prototype.removeStream = function(stream) {
-        var pc = this;
-        pc._senders = pc._senders || [];
-        origRemoveStream.apply(pc, [stream]);
-
-        stream.getTracks().forEach(function(track) {
-          var sender = pc._senders.find(function(s) {
-            return s.track === track;
-          });
-          if (sender) {
-            pc._senders.splice(pc._senders.indexOf(sender), 1); // remove sender
-          }
-        });
-      };
-    } else if (typeof window === 'object' && window.RTCPeerConnection &&
-               'getSenders' in window.RTCPeerConnection.prototype &&
-               'createDTMFSender' in window.RTCPeerConnection.prototype &&
-               window.RTCRtpSender &&
-               !('dtmf' in window.RTCRtpSender.prototype)) {
-      var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
-      window.RTCPeerConnection.prototype.getSenders = function() {
-        var pc = this;
-        var senders = origGetSenders.apply(pc, []);
-        senders.forEach(function(sender) {
-          sender._pc = pc;
-        });
-        return senders;
-      };
-
-      Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
-        get: function() {
-          if (this._dtmf === undefined) {
-            if (this.track.kind === 'audio') {
-              this._dtmf = this._pc.createDTMFSender(this.track);
-            } else {
-              this._dtmf = null;
-            }
-          }
-          return this._dtmf;
-        }
-      });
-    }
-  },
-
-  shimSourceObject: function(window) {
-    var URL = window && window.URL;
-
-    if (typeof window === 'object') {
-      if (window.HTMLMediaElement &&
-        !('srcObject' in window.HTMLMediaElement.prototype)) {
-        // Shim the srcObject property, once, when HTMLMediaElement is found.
-        Object.defineProperty(window.HTMLMediaElement.prototype, 'srcObject', {
-          get: function() {
-            return this._srcObject;
-          },
-          set: function(stream) {
-            var self = this;
-            // Use _srcObject as a private property for this shim
-            this._srcObject = stream;
-            if (this.src) {
-              URL.revokeObjectURL(this.src);
-            }
-
-            if (!stream) {
-              this.src = '';
-              return undefined;
-            }
-            this.src = URL.createObjectURL(stream);
-            // We need to recreate the blob url when a track is added or
-            // removed. Doing it manually since we want to avoid a recursion.
-            stream.addEventListener('addtrack', function() {
-              if (self.src) {
-                URL.revokeObjectURL(self.src);
-              }
-              self.src = URL.createObjectURL(stream);
-            });
-            stream.addEventListener('removetrack', function() {
-              if (self.src) {
-                URL.revokeObjectURL(self.src);
-              }
-              self.src = URL.createObjectURL(stream);
-            });
-          }
-        });
-      }
-    }
-  },
-
-  shimAddTrackRemoveTrack: function(window) {
-    var browserDetails = utils.detectBrowser(window);
-    // shim addTrack and removeTrack.
-    if (window.RTCPeerConnection.prototype.addTrack &&
-        browserDetails.version >= 63) {
-      return;
-    }
-
-    // also shim pc.getLocalStreams when addTrack is shimmed
-    // to return the original streams.
-    var origGetLocalStreams = window.RTCPeerConnection.prototype
-        .getLocalStreams;
-    window.RTCPeerConnection.prototype.getLocalStreams = function() {
-      var self = this;
-      var nativeStreams = origGetLocalStreams.apply(this);
-      self._reverseStreams = self._reverseStreams || {};
-      return nativeStreams.map(function(stream) {
-        return self._reverseStreams[stream.id];
-      });
-    };
-
-    var origAddStream = window.RTCPeerConnection.prototype.addStream;
-    window.RTCPeerConnection.prototype.addStream = function(stream) {
-      var pc = this;
-      pc._streams = pc._streams || {};
-      pc._reverseStreams = pc._reverseStreams || {};
-
-      stream.getTracks().forEach(function(track) {
-        var alreadyExists = pc.getSenders().find(function(s) {
-          return s.track === track;
-        });
-        if (alreadyExists) {
-          throw new DOMException('Track already exists.',
-              'InvalidAccessError');
-        }
-      });
-      // Add identity mapping for consistency with addTrack.
-      // Unless this is being used with a stream from addTrack.
-      if (!pc._reverseStreams[stream.id]) {
-        var newStream = new window.MediaStream(stream.getTracks());
-        pc._streams[stream.id] = newStream;
-        pc._reverseStreams[newStream.id] = stream;
-        stream = newStream;
-      }
-      origAddStream.apply(pc, [stream]);
-    };
-
-    var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
-    window.RTCPeerConnection.prototype.removeStream = function(stream) {
-      var pc = this;
-      pc._streams = pc._streams || {};
-      pc._reverseStreams = pc._reverseStreams || {};
-
-      origRemoveStream.apply(pc, [(pc._streams[stream.id] || stream)]);
-      delete pc._reverseStreams[(pc._streams[stream.id] ?
-          pc._streams[stream.id].id : stream.id)];
-      delete pc._streams[stream.id];
-    };
-
-    window.RTCPeerConnection.prototype.addTrack = function(track, stream) {
-      var pc = this;
-      if (pc.signalingState === 'closed') {
-        throw new DOMException(
-          'The RTCPeerConnection\'s signalingState is \'closed\'.',
-          'InvalidStateError');
-      }
-      var streams = [].slice.call(arguments, 1);
-      if (streams.length !== 1 ||
-          !streams[0].getTracks().find(function(t) {
-            return t === track;
-          })) {
-        // this is not fully correct but all we can manage without
-        // [[associated MediaStreams]] internal slot.
-        throw new DOMException(
-          'The adapter.js addTrack polyfill only supports a single ' +
-          ' stream which is associated with the specified track.',
-          'NotSupportedError');
-      }
-
-      var alreadyExists = pc.getSenders().find(function(s) {
-        return s.track === track;
-      });
-      if (alreadyExists) {
-        throw new DOMException('Track already exists.',
-            'InvalidAccessError');
-      }
-
-      pc._streams = pc._streams || {};
-      pc._reverseStreams = pc._reverseStreams || {};
-      var oldStream = pc._streams[stream.id];
-      if (oldStream) {
-        // this is using odd Chrome behaviour, use with caution:
-        // https://bugs.chromium.org/p/webrtc/issues/detail?id=7815
-        // Note: we rely on the high-level addTrack/dtmf shim to
-        // create the sender with a dtmf sender.
-        oldStream.addTrack(track);
-
-        // Trigger ONN async.
-        Promise.resolve().then(function() {
-          pc.dispatchEvent(new Event('negotiationneeded'));
-        });
-      } else {
-        var newStream = new window.MediaStream([track]);
-        pc._streams[stream.id] = newStream;
-        pc._reverseStreams[newStream.id] = stream;
-        pc.addStream(newStream);
-      }
-      return pc.getSenders().find(function(s) {
-        return s.track === track;
-      });
-    };
-
-    // replace the internal stream id with the external one and
-    // vice versa.
-    function replaceInternalStreamId(pc, description) {
-      var sdp = description.sdp;
-      Object.keys(pc._reverseStreams || []).forEach(function(internalId) {
-        var externalStream = pc._reverseStreams[internalId];
-        var internalStream = pc._streams[externalStream.id];
-        sdp = sdp.replace(new RegExp(internalStream.id, 'g'),
-            externalStream.id);
-      });
-      return new RTCSessionDescription({
-        type: description.type,
-        sdp: sdp
-      });
-    }
-    function replaceExternalStreamId(pc, description) {
-      var sdp = description.sdp;
-      Object.keys(pc._reverseStreams || []).forEach(function(internalId) {
-        var externalStream = pc._reverseStreams[internalId];
-        var internalStream = pc._streams[externalStream.id];
-        sdp = sdp.replace(new RegExp(externalStream.id, 'g'),
-            internalStream.id);
-      });
-      return new RTCSessionDescription({
-        type: description.type,
-        sdp: sdp
-      });
-    }
-    ['createOffer', 'createAnswer'].forEach(function(method) {
-      var nativeMethod = window.RTCPeerConnection.prototype[method];
-      window.RTCPeerConnection.prototype[method] = function() {
-        var pc = this;
-        var args = arguments;
-        var isLegacyCall = arguments.length &&
-            typeof arguments[0] === 'function';
-        if (isLegacyCall) {
-          return nativeMethod.apply(pc, [
-            function(description) {
-              var desc = replaceInternalStreamId(pc, description);
-              args[0].apply(null, [desc]);
-            },
-            function(err) {
-              if (args[1]) {
-                args[1].apply(null, err);
-              }
-            }, arguments[2]
-          ]);
-        }
-        return nativeMethod.apply(pc, arguments)
-        .then(function(description) {
-          return replaceInternalStreamId(pc, description);
-        });
-      };
-    });
-
-    var origSetLocalDescription =
-        window.RTCPeerConnection.prototype.setLocalDescription;
-    window.RTCPeerConnection.prototype.setLocalDescription = function() {
-      var pc = this;
-      if (!arguments.length || !arguments[0].type) {
-        return origSetLocalDescription.apply(pc, arguments);
-      }
-      arguments[0] = replaceExternalStreamId(pc, arguments[0]);
-      return origSetLocalDescription.apply(pc, arguments);
-    };
-
-    // TODO: mangle getStats: https://w3c.github.io/webrtc-stats/#dom-rtcmediastreamstats-streamidentifier
-
-    var origLocalDescription = Object.getOwnPropertyDescriptor(
-        window.RTCPeerConnection.prototype, 'localDescription');
-    Object.defineProperty(window.RTCPeerConnection.prototype,
-        'localDescription', {
-          get: function() {
-            var pc = this;
-            var description = origLocalDescription.get.apply(this);
-            if (description.type === '') {
-              return description;
-            }
-            return replaceInternalStreamId(pc, description);
-          }
-        });
-
-    window.RTCPeerConnection.prototype.removeTrack = function(sender) {
-      var pc = this;
-      if (pc.signalingState === 'closed') {
-        throw new DOMException(
-          'The RTCPeerConnection\'s signalingState is \'closed\'.',
-          'InvalidStateError');
-      }
-      // We can not yet check for sender instanceof RTCRtpSender
-      // since we shim RTPSender. So we check if sender._pc is set.
-      if (!sender._pc) {
-        throw new DOMException('Argument 1 of RTCPeerConnection.removeTrack ' +
-            'does not implement interface RTCRtpSender.', 'TypeError');
-      }
-      var isLocal = sender._pc === pc;
-      if (!isLocal) {
-        throw new DOMException('Sender was not created by this connection.',
-            'InvalidAccessError');
-      }
-
-      // Search for the native stream the senders track belongs to.
-      pc._streams = pc._streams || {};
-      var stream;
-      Object.keys(pc._streams).forEach(function(streamid) {
-        var hasTrack = pc._streams[streamid].getTracks().find(function(track) {
-          return sender.track === track;
-        });
-        if (hasTrack) {
-          stream = pc._streams[streamid];
-        }
-      });
-
-      if (stream) {
-        if (stream.getTracks().length === 1) {
-          // if this is the last track of the stream, remove the stream. This
-          // takes care of any shimmed _senders.
-          pc.removeStream(pc._reverseStreams[stream.id]);
-        } else {
-          // relying on the same odd chrome behaviour as above.
-          stream.removeTrack(sender.track);
-        }
-        pc.dispatchEvent(new Event('negotiationneeded'));
-      }
-    };
-  },
-
-  shimPeerConnection: function(window) {
-    var browserDetails = utils.detectBrowser(window);
-
-    // The RTCPeerConnection object.
-    if (!window.RTCPeerConnection) {
-      window.RTCPeerConnection = function(pcConfig, pcConstraints) {
-        // Translate iceTransportPolicy to iceTransports,
-        // see https://code.google.com/p/webrtc/issues/detail?id=4869
-        // this was fixed in M56 along with unprefixing RTCPeerConnection.
-        logging('PeerConnection');
-        if (pcConfig && pcConfig.iceTransportPolicy) {
-          pcConfig.iceTransports = pcConfig.iceTransportPolicy;
-        }
-
-        return new window.webkitRTCPeerConnection(pcConfig, pcConstraints);
-      };
-      window.RTCPeerConnection.prototype =
-          window.webkitRTCPeerConnection.prototype;
-      // wrap static methods. Currently just generateCertificate.
-      if (window.webkitRTCPeerConnection.generateCertificate) {
-        Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
-          get: function() {
-            return window.webkitRTCPeerConnection.generateCertificate;
-          }
-        });
-      }
-    } else {
-      // migrate from non-spec RTCIceServer.url to RTCIceServer.urls
-      var OrigPeerConnection = window.RTCPeerConnection;
-      window.RTCPeerConnection = function(pcConfig, pcConstraints) {
-        if (pcConfig && pcConfig.iceServers) {
-          var newIceServers = [];
-          for (var i = 0; i < pcConfig.iceServers.length; i++) {
-            var server = pcConfig.iceServers[i];
-            if (!server.hasOwnProperty('urls') &&
-                server.hasOwnProperty('url')) {
-              utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls');
-              server = JSON.parse(JSON.stringify(server));
-              server.urls = server.url;
-              newIceServers.push(server);
-            } else {
-              newIceServers.push(pcConfig.iceServers[i]);
-            }
-          }
-          pcConfig.iceServers = newIceServers;
-        }
-        return new OrigPeerConnection(pcConfig, pcConstraints);
-      };
-      window.RTCPeerConnection.prototype = OrigPeerConnection.prototype;
-      // wrap static methods. Currently just generateCertificate.
-      Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
-        get: function() {
-          return OrigPeerConnection.generateCertificate;
-        }
-      });
-    }
-
-    var origGetStats = window.RTCPeerConnection.prototype.getStats;
-    window.RTCPeerConnection.prototype.getStats = function(selector,
-        successCallback, errorCallback) {
-      var self = this;
-      var args = arguments;
-
-      // If selector is a function then we are in the old style stats so just
-      // pass back the original getStats format to avoid breaking old users.
-      if (arguments.length > 0 && typeof selector === 'function') {
-        return origGetStats.apply(this, arguments);
-      }
-
-      // When spec-style getStats is supported, return those when called with
-      // either no arguments or the selector argument is null.
-      if (origGetStats.length === 0 && (arguments.length === 0 ||
-          typeof arguments[0] !== 'function')) {
-        return origGetStats.apply(this, []);
-      }
-
-      var fixChromeStats_ = function(response) {
-        var standardReport = {};
-        var reports = response.result();
-        reports.forEach(function(report) {
-          var standardStats = {
-            id: report.id,
-            timestamp: report.timestamp,
-            type: {
-              localcandidate: 'local-candidate',
-              remotecandidate: 'remote-candidate'
-            }[report.type] || report.type
-          };
-          report.names().forEach(function(name) {
-            standardStats[name] = report.stat(name);
-          });
-          standardReport[standardStats.id] = standardStats;
-        });
-
-        return standardReport;
-      };
-
-      // shim getStats with maplike support
-      var makeMapStats = function(stats) {
-        return new Map(Object.keys(stats).map(function(key) {
-          return [key, stats[key]];
-        }));
-      };
-
-      if (arguments.length >= 2) {
-        var successCallbackWrapper_ = function(response) {
-          args[1](makeMapStats(fixChromeStats_(response)));
-        };
-
-        return origGetStats.apply(this, [successCallbackWrapper_,
-          arguments[0]]);
-      }
-
-      // promise-support
-      return new Promise(function(resolve, reject) {
-        origGetStats.apply(self, [
-          function(response) {
-            resolve(makeMapStats(fixChromeStats_(response)));
-          }, reject]);
-      }).then(successCallback, errorCallback);
-    };
-
-    // add promise support -- natively available in Chrome 51
-    if (browserDetails.version < 51) {
-      ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
-          .forEach(function(method) {
-            var nativeMethod = window.RTCPeerConnection.prototype[method];
-            window.RTCPeerConnection.prototype[method] = function() {
-              var args = arguments;
-              var self = this;
-              var promise = new Promise(function(resolve, reject) {
-                nativeMethod.apply(self, [args[0], resolve, reject]);
-              });
-              if (args.length < 2) {
-                return promise;
-              }
-              return promise.then(function() {
-                args[1].apply(null, []);
-              },
-              function(err) {
-                if (args.length >= 3) {
-                  args[2].apply(null, [err]);
-                }
-              });
-            };
-          });
-    }
-
-    // promise support for createOffer and createAnswer. Available (without
-    // bugs) since M52: crbug/619289
-    if (browserDetails.version < 52) {
-      ['createOffer', 'createAnswer'].forEach(function(method) {
-        var nativeMethod = window.RTCPeerConnection.prototype[method];
-        window.RTCPeerConnection.prototype[method] = function() {
-          var self = this;
-          if (arguments.length < 1 || (arguments.length === 1 &&
-              typeof arguments[0] === 'object')) {
-            var opts = arguments.length === 1 ? arguments[0] : undefined;
-            return new Promise(function(resolve, reject) {
-              nativeMethod.apply(self, [resolve, reject, opts]);
-            });
-          }
-          return nativeMethod.apply(this, arguments);
-        };
-      });
-    }
-
-    // shim implicit creation of RTCSessionDescription/RTCIceCandidate
-    ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
-        .forEach(function(method) {
-          var nativeMethod = window.RTCPeerConnection.prototype[method];
-          window.RTCPeerConnection.prototype[method] = function() {
-            arguments[0] = new ((method === 'addIceCandidate') ?
-                window.RTCIceCandidate :
-                window.RTCSessionDescription)(arguments[0]);
-            return nativeMethod.apply(this, arguments);
-          };
-        });
-
-    // support for addIceCandidate(null or undefined)
-    var nativeAddIceCandidate =
-        window.RTCPeerConnection.prototype.addIceCandidate;
-    window.RTCPeerConnection.prototype.addIceCandidate = function() {
-      if (!arguments[0]) {
-        if (arguments[1]) {
-          arguments[1].apply(null);
-        }
-        return Promise.resolve();
-      }
-      return nativeAddIceCandidate.apply(this, arguments);
-    };
-  }
-};
-
-
-// Expose public methods.
-module.exports = {
-  shimMediaStream: chromeShim.shimMediaStream,
-  shimOnTrack: chromeShim.shimOnTrack,
-  shimAddTrackRemoveTrack: chromeShim.shimAddTrackRemoveTrack,
-  shimGetSendersWithDtmf: chromeShim.shimGetSendersWithDtmf,
-  shimSourceObject: chromeShim.shimSourceObject,
-  shimPeerConnection: chromeShim.shimPeerConnection,
-  shimGetUserMedia: require('./getusermedia')
-};
-
-},{"../utils.js":13,"./getusermedia":6}],6:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
-var utils = require('../utils.js');
-var logging = utils.log;
-
-// Expose public methods.
-module.exports = function(window) {
-  var browserDetails = utils.detectBrowser(window);
-  var navigator = window && window.navigator;
-
-  var constraintsToChrome_ = function(c) {
-    if (typeof c !== 'object' || c.mandatory || c.optional) {
-      return c;
-    }
-    var cc = {};
-    Object.keys(c).forEach(function(key) {
-      if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
-        return;
-      }
-      var r = (typeof c[key] === 'object') ? c[key] : {ideal: c[key]};
-      if (r.exact !== undefined && typeof r.exact === 'number') {
-        r.min = r.max = r.exact;
-      }
-      var oldname_ = function(prefix, name) {
-        if (prefix) {
-          return prefix + name.charAt(0).toUpperCase() + name.slice(1);
-        }
-        return (name === 'deviceId') ? 'sourceId' : name;
-      };
-      if (r.ideal !== undefined) {
-        cc.optional = cc.optional || [];
-        var oc = {};
-        if (typeof r.ideal === 'number') {
-          oc[oldname_('min', key)] = r.ideal;
-          cc.optional.push(oc);
-          oc = {};
-          oc[oldname_('max', key)] = r.ideal;
-          cc.optional.push(oc);
-        } else {
-          oc[oldname_('', key)] = r.ideal;
-          cc.optional.push(oc);
-        }
-      }
-      if (r.exact !== undefined && typeof r.exact !== 'number') {
-        cc.mandatory = cc.mandatory || {};
-        cc.mandatory[oldname_('', key)] = r.exact;
-      } else {
-        ['min', 'max'].forEach(function(mix) {
-          if (r[mix] !== undefined) {
-            cc.mandatory = cc.mandatory || {};
-            cc.mandatory[oldname_(mix, key)] = r[mix];
-          }
-        });
-      }
-    });
-    if (c.advanced) {
-      cc.optional = (cc.optional || []).concat(c.advanced);
-    }
-    return cc;
-  };
-
-  var shimConstraints_ = function(constraints, func) {
-    if (browserDetails.version >= 61) {
-      return func(constraints);
-    }
-    constraints = JSON.parse(JSON.stringify(constraints));
-    if (constraints && typeof constraints.audio === 'object') {
-      var remap = function(obj, a, b) {
-        if (a in obj && !(b in obj)) {
-          obj[b] = obj[a];
-          delete obj[a];
-        }
-      };
-      constraints = JSON.parse(JSON.stringify(constraints));
-      remap(constraints.audio, 'autoGainControl', 'googAutoGainControl');
-      remap(constraints.audio, 'noiseSuppression', 'googNoiseSuppression');
-      constraints.audio = constraintsToChrome_(constraints.audio);
-    }
-    if (constraints && typeof constraints.video === 'object') {
-      // Shim facingMode for mobile & surface pro.
-      var face = constraints.video.facingMode;
-      face = face && ((typeof face === 'object') ? face : {ideal: face});
-      var getSupportedFacingModeLies = browserDetails.version < 66;
-
-      if ((face && (face.exact === 'user' || face.exact === 'environment' ||
-                    face.ideal === 'user' || face.ideal === 'environment')) &&
-          !(navigator.mediaDevices.getSupportedConstraints &&
-            navigator.mediaDevices.getSupportedConstraints().facingMode &&
-            !getSupportedFacingModeLies)) {
-        delete constraints.video.facingMode;
-        var matches;
-        if (face.exact === 'environment' || face.ideal === 'environment') {
-          matches = ['back', 'rear'];
-        } else if (face.exact === 'user' || face.ideal === 'user') {
-          matches = ['front'];
-        }
-        if (matches) {
-          // Look for matches in label, or use last cam for back (typical).
-          return navigator.mediaDevices.enumerateDevices()
-          .then(function(devices) {
-            devices = devices.filter(function(d) {
-              return d.kind === 'videoinput';
-            });
-            var dev = devices.find(function(d) {
-              return matches.some(function(match) {
-                return d.label.toLowerCase().indexOf(match) !== -1;
-              });
-            });
-            if (!dev && devices.length && matches.indexOf('back') !== -1) {
-              dev = devices[devices.length - 1]; // more likely the back cam
-            }
-            if (dev) {
-              constraints.video.deviceId = face.exact ? {exact: dev.deviceId} :
-                                                        {ideal: dev.deviceId};
-            }
-            constraints.video = constraintsToChrome_(constraints.video);
-            logging('chrome: ' + JSON.stringify(constraints));
-            return func(constraints);
-          });
-        }
-      }
-      constraints.video = constraintsToChrome_(constraints.video);
-    }
-    logging('chrome: ' + JSON.stringify(constraints));
-    return func(constraints);
-  };
-
-  var shimError_ = function(e) {
-    return {
-      name: {
-        PermissionDeniedError: 'NotAllowedError',
-        InvalidStateError: 'NotReadableError',
-        DevicesNotFoundError: 'NotFoundError',
-        ConstraintNotSatisfiedError: 'OverconstrainedError',
-        TrackStartError: 'NotReadableError',
-        MediaDeviceFailedDueToShutdown: 'NotReadableError',
-        MediaDeviceKillSwitchOn: 'NotReadableError'
-      }[e.name] || e.name,
-      message: e.message,
-      constraint: e.constraintName,
-      toString: function() {
-        return this.name + (this.message && ': ') + this.message;
-      }
-    };
-  };
-
-  var getUserMedia_ = function(constraints, onSuccess, onError) {
-    shimConstraints_(constraints, function(c) {
-      navigator.webkitGetUserMedia(c, onSuccess, function(e) {
-        if (onError) {
-          onError(shimError_(e));
-        }
-      });
-    });
-  };
-
-  navigator.getUserMedia = getUserMedia_;
-
-  // Returns the result of getUserMedia as a Promise.
-  var getUserMediaPromise_ = function(constraints) {
-    return new Promise(function(resolve, reject) {
-      navigator.getUserMedia(constraints, resolve, reject);
-    });
-  };
-
-  if (!navigator.mediaDevices) {
-    navigator.mediaDevices = {
-      getUserMedia: getUserMediaPromise_,
-      enumerateDevices: function() {
-        return new Promise(function(resolve) {
-          var kinds = {audio: 'audioinput', video: 'videoinput'};
-          return window.MediaStreamTrack.getSources(function(devices) {
-            resolve(devices.map(function(device) {
-              return {label: device.label,
-                kind: kinds[device.kind],
-                deviceId: device.id,
-                groupId: ''};
-            }));
-          });
-        });
-      },
-      getSupportedConstraints: function() {
-        return {
-          deviceId: true, echoCancellation: true, facingMode: true,
-          frameRate: true, height: true, width: true
-        };
-      }
-    };
-  }
-
-  // A shim for getUserMedia method on the mediaDevices object.
-  // TODO(KaptenJansson) remove once implemented in Chrome stable.
-  if (!navigator.mediaDevices.getUserMedia) {
-    navigator.mediaDevices.getUserMedia = function(constraints) {
-      return getUserMediaPromise_(constraints);
-    };
-  } else {
-    // Even though Chrome 45 has navigator.mediaDevices and a getUserMedia
-    // function which returns a Promise, it does not accept spec-style
-    // constraints.
-    var origGetUserMedia = navigator.mediaDevices.getUserMedia.
-        bind(navigator.mediaDevices);
-    navigator.mediaDevices.getUserMedia = function(cs) {
-      return shimConstraints_(cs, function(c) {
-        return origGetUserMedia(c).then(function(stream) {
-          if (c.audio && !stream.getAudioTracks().length ||
-              c.video && !stream.getVideoTracks().length) {
-            stream.getTracks().forEach(function(track) {
-              track.stop();
-            });
-            throw new DOMException('', 'NotFoundError');
-          }
-          return stream;
-        }, function(e) {
-          return Promise.reject(shimError_(e));
-        });
-      });
-    };
-  }
-
-  // Dummy devicechange event methods.
-  // TODO(KaptenJansson) remove once implemented in Chrome stable.
-  if (typeof navigator.mediaDevices.addEventListener === 'undefined') {
-    navigator.mediaDevices.addEventListener = function() {
-      logging('Dummy mediaDevices.addEventListener called.');
-    };
-  }
-  if (typeof navigator.mediaDevices.removeEventListener === 'undefined') {
-    navigator.mediaDevices.removeEventListener = function() {
-      logging('Dummy mediaDevices.removeEventListener called.');
-    };
-  }
-};
-
-},{"../utils.js":13}],7:[function(require,module,exports){
-/*
- *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
-
-var SDPUtils = require('sdp');
-var utils = require('./utils');
-
-// Wraps the peerconnection event eventNameToWrap in a function
-// which returns the modified event object.
-function wrapPeerConnectionEvent(window, eventNameToWrap, wrapper) {
-  if (!window.RTCPeerConnection) {
-    return;
-  }
-  var proto = window.RTCPeerConnection.prototype;
-  var nativeAddEventListener = proto.addEventListener;
-  proto.addEventListener = function(nativeEventName, cb) {
-    if (nativeEventName !== eventNameToWrap) {
-      return nativeAddEventListener.apply(this, arguments);
-    }
-    var wrappedCallback = function(e) {
-      cb(wrapper(e));
-    };
-    this._eventMap = this._eventMap || {};
-    this._eventMap[cb] = wrappedCallback;
-    return nativeAddEventListener.apply(this, [nativeEventName,
-      wrappedCallback]);
-  };
-
-  var nativeRemoveEventListener = proto.removeEventListener;
-  proto.removeEventListener = function(nativeEventName, cb) {
-    if (nativeEventName !== eventNameToWrap || !this._eventMap
-        || !this._eventMap[cb]) {
-      return nativeRemoveEventListener.apply(this, arguments);
-    }
-    var unwrappedCb = this._eventMap[cb];
-    delete this._eventMap[cb];
-    return nativeRemoveEventListener.apply(this, [nativeEventName,
-      unwrappedCb]);
-  };
-
-  Object.defineProperty(proto, 'on' + eventNameToWrap, {
-    get: function() {
-      return this['_on' + eventNameToWrap];
-    },
-    set: function(cb) {
-      if (this['_on' + eventNameToWrap]) {
-        this.removeEventListener(eventNameToWrap,
-            this['_on' + eventNameToWrap]);
-        delete this['_on' + eventNameToWrap];
-      }
-      if (cb) {
-        this.addEventListener(eventNameToWrap,
-            this['_on' + eventNameToWrap] = cb);
-      }
-    }
-  });
-}
-
-module.exports = {
-  shimRTCIceCandidate: function(window) {
-    // foundation is arbitrarily chosen as an indicator for full support for
-    // https://w3c.github.io/webrtc-pc/#rtcicecandidate-interface
-    if (window.RTCIceCandidate && 'foundation' in
-        window.RTCIceCandidate.prototype) {
-      return;
-    }
-
-    var NativeRTCIceCandidate = window.RTCIceCandidate;
-    window.RTCIceCandidate = function(args) {
-      // Remove the a= which shouldn't be part of the candidate string.
-      if (typeof args === 'object' && args.candidate &&
-          args.candidate.indexOf('a=') === 0) {
-        args = JSON.parse(JSON.stringify(args));
-        args.candidate = args.candidate.substr(2);
-      }
-
-      // Augment the native candidate with the parsed fields.
-      var nativeCandidate = new NativeRTCIceCandidate(args);
-      var parsedCandidate = SDPUtils.parseCandidate(args.candidate);
-      var augmentedCandidate = Object.assign(nativeCandidate,
-          parsedCandidate);
-
-      // Add a serializer that does not serialize the extra attributes.
-      augmentedCandidate.toJSON = function() {
-        return {
-          candidate: augmentedCandidate.candidate,
-          sdpMid: augmentedCandidate.sdpMid,
-          sdpMLineIndex: augmentedCandidate.sdpMLineIndex,
-          usernameFragment: augmentedCandidate.usernameFragment,
-        };
-      };
-      return augmentedCandidate;
-    };
-
-    // Hook up the augmented candidate in onicecandidate and
-    // addEventListener('icecandidate', ...)
-    wrapPeerConnectionEvent(window, 'icecandidate', function(e) {
-      if (e.candidate) {
-        Object.defineProperty(e, 'candidate', {
-          value: new window.RTCIceCandidate(e.candidate),
-          writable: 'false'
-        });
-      }
-      return e;
-    });
-  },
-
-  // shimCreateObjectURL must be called before shimSourceObject to avoid loop.
-
-  shimCreateObjectURL: function(window) {
-    var URL = window && window.URL;
-
-    if (!(typeof window === 'object' && window.HTMLMediaElement &&
-          'srcObject' in window.HTMLMediaElement.prototype &&
-        URL.createObjectURL && URL.revokeObjectURL)) {
-      // Only shim CreateObjectURL using srcObject if srcObject exists.
-      return undefined;
-    }
-
-    var nativeCreateObjectURL = URL.createObjectURL.bind(URL);
-    var nativeRevokeObjectURL = URL.revokeObjectURL.bind(URL);
-    var streams = new Map(), newId = 0;
-
-    URL.createObjectURL = function(stream) {
-      if ('getTracks' in stream) {
-        var url = 'polyblob:' + (++newId);
-        streams.set(url, stream);
-        utils.deprecated('URL.createObjectURL(stream)',
-            'elem.srcObject = stream');
-        return url;
-      }
-      return nativeCreateObjectURL(stream);
-    };
-    URL.revokeObjectURL = function(url) {
-      nativeRevokeObjectURL(url);
-      streams.delete(url);
-    };
-
-    var dsc = Object.getOwnPropertyDescriptor(window.HTMLMediaElement.prototype,
-                                              'src');
-    Object.defineProperty(window.HTMLMediaElement.prototype, 'src', {
-      get: function() {
-        return dsc.get.apply(this);
-      },
-      set: function(url) {
-        this.srcObject = streams.get(url) || null;
-        return dsc.set.apply(this, [url]);
-      }
-    });
-
-    var nativeSetAttribute = window.HTMLMediaElement.prototype.setAttribute;
-    window.HTMLMediaElement.prototype.setAttribute = function() {
-      if (arguments.length === 2 &&
-          ('' + arguments[0]).toLowerCase() === 'src') {
-        this.srcObject = streams.get(arguments[1]) || null;
-      }
-      return nativeSetAttribute.apply(this, arguments);
-    };
-  }
-};
-
-},{"./utils":13,"sdp":2}],8:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
-
-var utils = require('../utils');
-var shimRTCPeerConnection = require('rtcpeerconnection-shim');
-
-module.exports = {
-  shimGetUserMedia: require('./getusermedia'),
-  shimPeerConnection: function(window) {
-    var browserDetails = utils.detectBrowser(window);
-
-    if (window.RTCIceGatherer) {
-      // ORTC defines an RTCIceCandidate object but no constructor.
-      // Not implemented in Edge.
-      if (!window.RTCIceCandidate) {
-        window.RTCIceCandidate = function(args) {
-          return args;
-        };
-      }
-      // ORTC does not have a session description object but
-      // other browsers (i.e. Chrome) that will support both PC and ORTC
-      // in the future might have this defined already.
-      if (!window.RTCSessionDescription) {
-        window.RTCSessionDescription = function(args) {
-          return args;
-        };
-      }
-      // this adds an additional event listener to MediaStrackTrack that signals
-      // when a tracks enabled property was changed. Workaround for a bug in
-      // addStream, see below. No longer required in 15025+
-      if (browserDetails.version < 15025) {
-        var origMSTEnabled = Object.getOwnPropertyDescriptor(
-            window.MediaStreamTrack.prototype, 'enabled');
-        Object.defineProperty(window.MediaStreamTrack.prototype, 'enabled', {
-          set: function(value) {
-            origMSTEnabled.set.call(this, value);
-            var ev = new Event('enabled');
-            ev.enabled = value;
-            this.dispatchEvent(ev);
-          }
-        });
-      }
-    }
-
-    // ORTC defines the DTMF sender a bit different.
-    // https://github.com/w3c/ortc/issues/714
-    if (window.RTCRtpSender && !('dtmf' in window.RTCRtpSender.prototype)) {
-      Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
-        get: function() {
-          if (this._dtmf === undefined) {
-            if (this.track.kind === 'audio') {
-              this._dtmf = new window.RTCDtmfSender(this);
-            } else if (this.track.kind === 'video') {
-              this._dtmf = null;
-            }
-          }
-          return this._dtmf;
-        }
-      });
-    }
-
-    window.RTCPeerConnection =
-        shimRTCPeerConnection(window, browserDetails.version);
-  },
-  shimReplaceTrack: function(window) {
-    // ORTC has replaceTrack -- https://github.com/w3c/ortc/issues/614
-    if (window.RTCRtpSender &&
-        !('replaceTrack' in window.RTCRtpSender.prototype)) {
-      window.RTCRtpSender.prototype.replaceTrack =
-          window.RTCRtpSender.prototype.setTrack;
-    }
-  }
-};
-
-},{"../utils":13,"./getusermedia":9,"rtcpeerconnection-shim":1}],9:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
-
-// Expose public methods.
-module.exports = function(window) {
-  var navigator = window && window.navigator;
-
-  var shimError_ = function(e) {
-    return {
-      name: {PermissionDeniedError: 'NotAllowedError'}[e.name] || e.name,
-      message: e.message,
-      constraint: e.constraint,
-      toString: function() {
-        return this.name;
-      }
-    };
-  };
-
-  // getUserMedia error shim.
-  var origGetUserMedia = navigator.mediaDevices.getUserMedia.
-      bind(navigator.mediaDevices);
-  navigator.mediaDevices.getUserMedia = function(c) {
-    return origGetUserMedia(c).catch(function(e) {
-      return Promise.reject(shimError_(e));
-    });
-  };
-};
-
-},{}],10:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
-
-var utils = require('../utils');
-
-var firefoxShim = {
-  shimOnTrack: function(window) {
-    if (typeof window === 'object' && window.RTCPeerConnection && !('ontrack' in
-        window.RTCPeerConnection.prototype)) {
-      Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
-        get: function() {
-          return this._ontrack;
-        },
-        set: function(f) {
-          if (this._ontrack) {
-            this.removeEventListener('track', this._ontrack);
-            this.removeEventListener('addstream', this._ontrackpoly);
-          }
-          this.addEventListener('track', this._ontrack = f);
-          this.addEventListener('addstream', this._ontrackpoly = function(e) {
-            e.stream.getTracks().forEach(function(track) {
-              var event = new Event('track');
-              event.track = track;
-              event.receiver = {track: track};
-              event.transceiver = {receiver: event.receiver};
-              event.streams = [e.stream];
-              this.dispatchEvent(event);
-            }.bind(this));
-          }.bind(this));
-        }
-      });
-    }
-    if (typeof window === 'object' && window.RTCTrackEvent &&
-        ('receiver' in window.RTCTrackEvent.prototype) &&
-        !('transceiver' in window.RTCTrackEvent.prototype)) {
-      Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
-        get: function() {
-          return {receiver: this.receiver};
-        }
-      });
-    }
-  },
-
-  shimSourceObject: function(window) {
-    // Firefox has supported mozSrcObject since FF22, unprefixed in 42.
-    if (typeof window === 'object') {
-      if (window.HTMLMediaElement &&
-        !('srcObject' in window.HTMLMediaElement.prototype)) {
-        // Shim the srcObject property, once, when HTMLMediaElement is found.
-        Object.defineProperty(window.HTMLMediaElement.prototype, 'srcObject', {
-          get: function() {
-            return this.mozSrcObject;
-          },
-          set: function(stream) {
-            this.mozSrcObject = stream;
-          }
-        });
-      }
-    }
-  },
-
-  shimPeerConnection: function(window) {
-    var browserDetails = utils.detectBrowser(window);
-
-    if (typeof window !== 'object' || !(window.RTCPeerConnection ||
-        window.mozRTCPeerConnection)) {
-      return; // probably media.peerconnection.enabled=false in about:config
-    }
-    // The RTCPeerConnection object.
-    if (!window.RTCPeerConnection) {
-      window.RTCPeerConnection = function(pcConfig, pcConstraints) {
-        if (browserDetails.version < 38) {
-          // .urls is not supported in FF < 38.
-          // create RTCIceServers with a single url.
-          if (pcConfig && pcConfig.iceServers) {
-            var newIceServers = [];
-            for (var i = 0; i < pcConfig.iceServers.length; i++) {
-              var server = pcConfig.iceServers[i];
-              if (server.hasOwnProperty('urls')) {
-                for (var j = 0; j < server.urls.length; j++) {
-                  var newServer = {
-                    url: server.urls[j]
-                  };
-                  if (server.urls[j].indexOf('turn') === 0) {
-                    newServer.username = server.username;
-                    newServer.credential = server.credential;
-                  }
-                  newIceServers.push(newServer);
-                }
-              } else {
-                newIceServers.push(pcConfig.iceServers[i]);
-              }
-            }
-            pcConfig.iceServers = newIceServers;
-          }
-        }
-        return new window.mozRTCPeerConnection(pcConfig, pcConstraints);
-      };
-      window.RTCPeerConnection.prototype =
-          window.mozRTCPeerConnection.prototype;
-
-      // wrap static methods. Currently just generateCertificate.
-      if (window.mozRTCPeerConnection.generateCertificate) {
-        Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
-          get: function() {
-            return window.mozRTCPeerConnection.generateCertificate;
-          }
-        });
-      }
-
-      window.RTCSessionDescription = window.mozRTCSessionDescription;
-      window.RTCIceCandidate = window.mozRTCIceCandidate;
-    }
-
-    // shim away need for obsolete RTCIceCandidate/RTCSessionDescription.
-    ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
-        .forEach(function(method) {
-          var nativeMethod = window.RTCPeerConnection.prototype[method];
-          window.RTCPeerConnection.prototype[method] = function() {
-            arguments[0] = new ((method === 'addIceCandidate') ?
-                window.RTCIceCandidate :
-                window.RTCSessionDescription)(arguments[0]);
-            return nativeMethod.apply(this, arguments);
-          };
-        });
-
-    // support for addIceCandidate(null or undefined)
-    var nativeAddIceCandidate =
-        window.RTCPeerConnection.prototype.addIceCandidate;
-    window.RTCPeerConnection.prototype.addIceCandidate = function() {
-      if (!arguments[0]) {
-        if (arguments[1]) {
-          arguments[1].apply(null);
-        }
-        return Promise.resolve();
-      }
-      return nativeAddIceCandidate.apply(this, arguments);
-    };
-
-    // shim getStats with maplike support
-    var makeMapStats = function(stats) {
-      var map = new Map();
-      Object.keys(stats).forEach(function(key) {
-        map.set(key, stats[key]);
-        map[key] = stats[key];
-      });
-      return map;
-    };
-
-    var modernStatsTypes = {
-      inboundrtp: 'inbound-rtp',
-      outboundrtp: 'outbound-rtp',
-      candidatepair: 'candidate-pair',
-      localcandidate: 'local-candidate',
-      remotecandidate: 'remote-candidate'
-    };
-
-    var nativeGetStats = window.RTCPeerConnection.prototype.getStats;
-    window.RTCPeerConnection.prototype.getStats = function(
-      selector,
-      onSucc,
-      onErr
-    ) {
-      return nativeGetStats.apply(this, [selector || null])
-        .then(function(stats) {
-          if (browserDetails.version < 48) {
-            stats = makeMapStats(stats);
-          }
-          if (browserDetails.version < 53 && !onSucc) {
-            // Shim only promise getStats with spec-hyphens in type names
-            // Leave callback version alone; misc old uses of forEach before Map
-            try {
-              stats.forEach(function(stat) {
-                stat.type = modernStatsTypes[stat.type] || stat.type;
-              });
-            } catch (e) {
-              if (e.name !== 'TypeError') {
-                throw e;
-              }
-              // Avoid TypeError: "type" is read-only, in old versions. 34-43ish
-              stats.forEach(function(stat, i) {
-                stats.set(i, Object.assign({}, stat, {
-                  type: modernStatsTypes[stat.type] || stat.type
-                }));
-              });
-            }
-          }
-          return stats;
-        })
-        .then(onSucc, onErr);
-    };
-  },
-
-  shimRemoveStream: function(window) {
-    if ('removeStream' in window.RTCPeerConnection.prototype) {
-      return;
-    }
-    window.RTCPeerConnection.prototype.removeStream = function(stream) {
-      utils.deprecated('removeStream', 'removeTrack');
-      this.getSenders().forEach(function(sender) {
-        if (sender.track && stream.getTracks().indexOf(sender.track) !== -1) {
-          this.removeTrack(sender);
-        }
-      });
-    };
-  }
-};
-
-// Expose public methods.
-module.exports = {
-  shimOnTrack: firefoxShim.shimOnTrack,
-  shimSourceObject: firefoxShim.shimSourceObject,
-  shimPeerConnection: firefoxShim.shimPeerConnection,
-  shimRemoveStream: firefoxShim.shimRemoveStream,
-  shimGetUserMedia: require('./getusermedia')
-};
-
-},{"../utils":13,"./getusermedia":11}],11:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
-
-var utils = require('../utils');
-var logging = utils.log;
-
-// Expose public methods.
-module.exports = function(window) {
-  var browserDetails = utils.detectBrowser(window);
-  var navigator = window && window.navigator;
-  var MediaStreamTrack = window && window.MediaStreamTrack;
-
-  var shimError_ = function(e) {
-    return {
-      name: {
-        InternalError: 'NotReadableError',
-        NotSupportedError: 'TypeError',
-        PermissionDeniedError: 'NotAllowedError',
-        SecurityError: 'NotAllowedError'
-      }[e.name] || e.name,
-      message: {
-        'The operation is insecure.': 'The request is not allowed by the ' +
-        'user agent or the platform in the current context.'
-      }[e.message] || e.message,
-      constraint: e.constraint,
-      toString: function() {
-        return this.name + (this.message && ': ') + this.message;
-      }
-    };
-  };
-
-  // getUserMedia constraints shim.
-  var getUserMedia_ = function(constraints, onSuccess, onError) {
-    var constraintsToFF37_ = function(c) {
-      if (typeof c !== 'object' || c.require) {
-        return c;
-      }
-      var require = [];
-      Object.keys(c).forEach(function(key) {
-        if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
-          return;
-        }
-        var r = c[key] = (typeof c[key] === 'object') ?
-            c[key] : {ideal: c[key]};
-        if (r.min !== undefined ||
-            r.max !== undefined || r.exact !== undefined) {
-          require.push(key);
-        }
-        if (r.exact !== undefined) {
-          if (typeof r.exact === 'number') {
-            r. min = r.max = r.exact;
-          } else {
-            c[key] = r.exact;
-          }
-          delete r.exact;
-        }
-        if (r.ideal !== undefined) {
-          c.advanced = c.advanced || [];
-          var oc = {};
-          if (typeof r.ideal === 'number') {
-            oc[key] = {min: r.ideal, max: r.ideal};
-          } else {
-            oc[key] = r.ideal;
-          }
-          c.advanced.push(oc);
-          delete r.ideal;
-          if (!Object.keys(r).length) {
-            delete c[key];
-          }
-        }
-      });
-      if (require.length) {
-        c.require = require;
-      }
-      return c;
-    };
-    constraints = JSON.parse(JSON.stringify(constraints));
-    if (browserDetails.version < 38) {
-      logging('spec: ' + JSON.stringify(constraints));
-      if (constraints.audio) {
-        constraints.audio = constraintsToFF37_(constraints.audio);
-      }
-      if (constraints.video) {
-        constraints.video = constraintsToFF37_(constraints.video);
-      }
-      logging('ff37: ' + JSON.stringify(constraints));
-    }
-    return navigator.mozGetUserMedia(constraints, onSuccess, function(e) {
-      onError(shimError_(e));
-    });
-  };
-
-  // Returns the result of getUserMedia as a Promise.
-  var getUserMediaPromise_ = function(constraints) {
-    return new Promise(function(resolve, reject) {
-      getUserMedia_(constraints, resolve, reject);
-    });
-  };
-
-  // Shim for mediaDevices on older versions.
-  if (!navigator.mediaDevices) {
-    navigator.mediaDevices = {getUserMedia: getUserMediaPromise_,
-      addEventListener: function() { },
-      removeEventListener: function() { }
-    };
-  }
-  navigator.mediaDevices.enumerateDevices =
-      navigator.mediaDevices.enumerateDevices || function() {
-        return new Promise(function(resolve) {
-          var infos = [
-            {kind: 'audioinput', deviceId: 'default', label: '', groupId: ''},
-            {kind: 'videoinput', deviceId: 'default', label: '', groupId: ''}
-          ];
-          resolve(infos);
-        });
-      };
-
-  if (browserDetails.version < 41) {
-    // Work around http://bugzil.la/1169665
-    var orgEnumerateDevices =
-        navigator.mediaDevices.enumerateDevices.bind(navigator.mediaDevices);
-    navigator.mediaDevices.enumerateDevices = function() {
-      return orgEnumerateDevices().then(undefined, function(e) {
-        if (e.name === 'NotFoundError') {
-          return [];
-        }
-        throw e;
-      });
-    };
-  }
-  if (browserDetails.version < 49) {
-    var origGetUserMedia = navigator.mediaDevices.getUserMedia.
-        bind(navigator.mediaDevices);
-    navigator.mediaDevices.getUserMedia = function(c) {
-      return origGetUserMedia(c).then(function(stream) {
-        // Work around https://bugzil.la/802326
-        if (c.audio && !stream.getAudioTracks().length ||
-            c.video && !stream.getVideoTracks().length) {
-          stream.getTracks().forEach(function(track) {
-            track.stop();
-          });
-          throw new DOMException('The object can not be found here.',
-                                 'NotFoundError');
-        }
-        return stream;
-      }, function(e) {
-        return Promise.reject(shimError_(e));
-      });
-    };
-  }
-  if (!(browserDetails.version > 55 &&
-      'autoGainControl' in navigator.mediaDevices.getSupportedConstraints())) {
-    var remap = function(obj, a, b) {
-      if (a in obj && !(b in obj)) {
-        obj[b] = obj[a];
-        delete obj[a];
-      }
-    };
-
-    var nativeGetUserMedia = navigator.mediaDevices.getUserMedia.
-        bind(navigator.mediaDevices);
-    navigator.mediaDevices.getUserMedia = function(c) {
-      if (typeof c === 'object' && typeof c.audio === 'object') {
-        c = JSON.parse(JSON.stringify(c));
-        remap(c.audio, 'autoGainControl', 'mozAutoGainControl');
-        remap(c.audio, 'noiseSuppression', 'mozNoiseSuppression');
-      }
-      return nativeGetUserMedia(c);
-    };
-
-    if (MediaStreamTrack && MediaStreamTrack.prototype.getSettings) {
-      var nativeGetSettings = MediaStreamTrack.prototype.getSettings;
-      MediaStreamTrack.prototype.getSettings = function() {
-        var obj = nativeGetSettings.apply(this, arguments);
-        remap(obj, 'mozAutoGainControl', 'autoGainControl');
-        remap(obj, 'mozNoiseSuppression', 'noiseSuppression');
-        return obj;
-      };
-    }
-
-    if (MediaStreamTrack && MediaStreamTrack.prototype.applyConstraints) {
-      var nativeApplyConstraints = MediaStreamTrack.prototype.applyConstraints;
-      MediaStreamTrack.prototype.applyConstraints = function(c) {
-        if (this.kind === 'audio' && typeof c === 'object') {
-          c = JSON.parse(JSON.stringify(c));
-          remap(c, 'autoGainControl', 'mozAutoGainControl');
-          remap(c, 'noiseSuppression', 'mozNoiseSuppression');
-        }
-        return nativeApplyConstraints.apply(this, [c]);
-      };
-    }
-  }
-  navigator.getUserMedia = function(constraints, onSuccess, onError) {
-    if (browserDetails.version < 44) {
-      return getUserMedia_(constraints, onSuccess, onError);
-    }
-    // Replace Firefox 44+'s deprecation warning with unprefixed version.
-    utils.deprecated('navigator.getUserMedia',
-        'navigator.mediaDevices.getUserMedia');
-    navigator.mediaDevices.getUserMedia(constraints).then(onSuccess, onError);
-  };
-};
-
-},{"../utils":13}],12:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
-'use strict';
-var utils = require('../utils');
-
-var safariShim = {
-  // TODO: DrAlex, should be here, double check against LayoutTests
-
-  // TODO: once the back-end for the mac port is done, add.
-  // TODO: check for webkitGTK+
-  // shimPeerConnection: function() { },
-
-  shimLocalStreamsAPI: function(window) {
-    if (typeof window !== 'object' || !window.RTCPeerConnection) {
-      return;
-    }
-    if (!('getLocalStreams' in window.RTCPeerConnection.prototype)) {
-      window.RTCPeerConnection.prototype.getLocalStreams = function() {
-        if (!this._localStreams) {
-          this._localStreams = [];
-        }
-        return this._localStreams;
-      };
-    }
-    if (!('getStreamById' in window.RTCPeerConnection.prototype)) {
-      window.RTCPeerConnection.prototype.getStreamById = function(id) {
-        var result = null;
-        if (this._localStreams) {
-          this._localStreams.forEach(function(stream) {
-            if (stream.id === id) {
-              result = stream;
-            }
-          });
-        }
-        if (this._remoteStreams) {
-          this._remoteStreams.forEach(function(stream) {
-            if (stream.id === id) {
-              result = stream;
-            }
-          });
-        }
-        return result;
-      };
-    }
-    if (!('addStream' in window.RTCPeerConnection.prototype)) {
-      var _addTrack = window.RTCPeerConnection.prototype.addTrack;
-      window.RTCPeerConnection.prototype.addStream = function(stream) {
-        if (!this._localStreams) {
-          this._localStreams = [];
-        }
-        if (this._localStreams.indexOf(stream) === -1) {
-          this._localStreams.push(stream);
-        }
-        var self = this;
-        stream.getTracks().forEach(function(track) {
-          _addTrack.call(self, track, stream);
-        });
-      };
-
-      window.RTCPeerConnection.prototype.addTrack = function(track, stream) {
-        if (stream) {
-          if (!this._localStreams) {
-            this._localStreams = [stream];
-          } else if (this._localStreams.indexOf(stream) === -1) {
-            this._localStreams.push(stream);
-          }
-        }
-        _addTrack.call(this, track, stream);
-      };
-    }
-    if (!('removeStream' in window.RTCPeerConnection.prototype)) {
-      window.RTCPeerConnection.prototype.removeStream = function(stream) {
-        if (!this._localStreams) {
-          this._localStreams = [];
-        }
-        var index = this._localStreams.indexOf(stream);
-        if (index === -1) {
-          return;
-        }
-        this._localStreams.splice(index, 1);
-        var self = this;
-        var tracks = stream.getTracks();
-        this.getSenders().forEach(function(sender) {
-          if (tracks.indexOf(sender.track) !== -1) {
-            self.removeTrack(sender);
-          }
-        });
-      };
-    }
-  },
-  shimRemoteStreamsAPI: function(window) {
-    if (typeof window !== 'object' || !window.RTCPeerConnection) {
-      return;
-    }
-    if (!('getRemoteStreams' in window.RTCPeerConnection.prototype)) {
-      window.RTCPeerConnection.prototype.getRemoteStreams = function() {
-        return this._remoteStreams ? this._remoteStreams : [];
-      };
-    }
-    if (!('onaddstream' in window.RTCPeerConnection.prototype)) {
-      Object.defineProperty(window.RTCPeerConnection.prototype, 'onaddstream', {
-        get: function() {
-          return this._onaddstream;
-        },
-        set: function(f) {
-          if (this._onaddstream) {
-            this.removeEventListener('addstream', this._onaddstream);
-            this.removeEventListener('track', this._onaddstreampoly);
-          }
-          this.addEventListener('addstream', this._onaddstream = f);
-          this.addEventListener('track', this._onaddstreampoly = function(e) {
-            var stream = e.streams[0];
-            if (!this._remoteStreams) {
-              this._remoteStreams = [];
-            }
-            if (this._remoteStreams.indexOf(stream) >= 0) {
-              return;
-            }
-            this._remoteStreams.push(stream);
-            var event = new Event('addstream');
-            event.stream = e.streams[0];
-            this.dispatchEvent(event);
-          }.bind(this));
-        }
-      });
-    }
-  },
-  shimCallbacksAPI: function(window) {
-    if (typeof window !== 'object' || !window.RTCPeerConnection) {
-      return;
-    }
-    var prototype = window.RTCPeerConnection.prototype;
-    var createOffer = prototype.createOffer;
-    var createAnswer = prototype.createAnswer;
-    var setLocalDescription = prototype.setLocalDescription;
-    var setRemoteDescription = prototype.setRemoteDescription;
-    var addIceCandidate = prototype.addIceCandidate;
-
-    prototype.createOffer = function(successCallback, failureCallback) {
-      var options = (arguments.length >= 2) ? arguments[2] : arguments[0];
-      var promise = createOffer.apply(this, [options]);
-      if (!failureCallback) {
-        return promise;
-      }
-      promise.then(successCallback, failureCallback);
-      return Promise.resolve();
-    };
-
-    prototype.createAnswer = function(successCallback, failureCallback) {
-      var options = (arguments.length >= 2) ? arguments[2] : arguments[0];
-      var promise = createAnswer.apply(this, [options]);
-      if (!failureCallback) {
-        return promise;
-      }
-      promise.then(successCallback, failureCallback);
-      return Promise.resolve();
-    };
-
-    var withCallback = function(description, successCallback, failureCallback) {
-      var promise = setLocalDescription.apply(this, [description]);
-      if (!failureCallback) {
-        return promise;
-      }
-      promise.then(successCallback, failureCallback);
-      return Promise.resolve();
-    };
-    prototype.setLocalDescription = withCallback;
-
-    withCallback = function(description, successCallback, failureCallback) {
-      var promise = setRemoteDescription.apply(this, [description]);
-      if (!failureCallback) {
-        return promise;
-      }
-      promise.then(successCallback, failureCallback);
-      return Promise.resolve();
-    };
-    prototype.setRemoteDescription = withCallback;
-
-    withCallback = function(candidate, successCallback, failureCallback) {
-      var promise = addIceCandidate.apply(this, [candidate]);
-      if (!failureCallback) {
-        return promise;
-      }
-      promise.then(successCallback, failureCallback);
-      return Promise.resolve();
-    };
-    prototype.addIceCandidate = withCallback;
-  },
-  shimGetUserMedia: function(window) {
-    var navigator = window && window.navigator;
-
-    if (!navigator.getUserMedia) {
-      if (navigator.webkitGetUserMedia) {
-        navigator.getUserMedia = navigator.webkitGetUserMedia.bind(navigator);
-      } else if (navigator.mediaDevices &&
-          navigator.mediaDevices.getUserMedia) {
-        navigator.getUserMedia = function(constraints, cb, errcb) {
-          navigator.mediaDevices.getUserMedia(constraints)
-          .then(cb, errcb);
-        }.bind(navigator);
-      }
-    }
-  },
-  shimRTCIceServerUrls: function(window) {
-    // migrate from non-spec RTCIceServer.url to RTCIceServer.urls
-    var OrigPeerConnection = window.RTCPeerConnection;
-    window.RTCPeerConnection = function(pcConfig, pcConstraints) {
-      if (pcConfig && pcConfig.iceServers) {
-        var newIceServers = [];
-        for (var i = 0; i < pcConfig.iceServers.length; i++) {
-          var server = pcConfig.iceServers[i];
-          if (!server.hasOwnProperty('urls') &&
-              server.hasOwnProperty('url')) {
-            utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls');
-            server = JSON.parse(JSON.stringify(server));
-            server.urls = server.url;
-            delete server.url;
-            newIceServers.push(server);
-          } else {
-            newIceServers.push(pcConfig.iceServers[i]);
-          }
-        }
-        pcConfig.iceServers = newIceServers;
-      }
-      return new OrigPeerConnection(pcConfig, pcConstraints);
-    };
-    window.RTCPeerConnection.prototype = OrigPeerConnection.prototype;
-    // wrap static methods. Currently just generateCertificate.
-    if ('generateCertificate' in window.RTCPeerConnection) {
-      Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
-        get: function() {
-          return OrigPeerConnection.generateCertificate;
-        }
-      });
-    }
-  },
-  shimTrackEventTransceiver: function(window) {
-    // Add event.transceiver member over deprecated event.receiver
-    if (typeof window === 'object' && window.RTCPeerConnection &&
-        ('receiver' in window.RTCTrackEvent.prototype) &&
-        // can't check 'transceiver' in window.RTCTrackEvent.prototype, as it is
-        // defined for some reason even when window.RTCTransceiver is not.
-        !window.RTCTransceiver) {
-      Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
-        get: function() {
-          return {receiver: this.receiver};
-        }
-      });
-    }
-  },
-
-  shimCreateOfferLegacy: function(window) {
-    var origCreateOffer = window.RTCPeerConnection.prototype.createOffer;
-    window.RTCPeerConnection.prototype.createOffer = function(offerOptions) {
-      var pc = this;
-      if (offerOptions) {
-        var audioTransceiver = pc.getTransceivers().find(function(transceiver) {
-          return transceiver.sender.track &&
-              transceiver.sender.track.kind === 'audio';
-        });
-        if (offerOptions.offerToReceiveAudio === false && audioTransceiver) {
-          if (audioTransceiver.direction === 'sendrecv') {
-            audioTransceiver.setDirection('sendonly');
-          } else if (audioTransceiver.direction === 'recvonly') {
-            audioTransceiver.setDirection('inactive');
-          }
-        } else if (offerOptions.offerToReceiveAudio === true &&
-            !audioTransceiver) {
-          pc.addTransceiver('audio');
-        }
-
-        var videoTransceiver = pc.getTransceivers().find(function(transceiver) {
-          return transceiver.sender.track &&
-              transceiver.sender.track.kind === 'video';
-        });
-        if (offerOptions.offerToReceiveVideo === false && videoTransceiver) {
-          if (videoTransceiver.direction === 'sendrecv') {
-            videoTransceiver.setDirection('sendonly');
-          } else if (videoTransceiver.direction === 'recvonly') {
-            videoTransceiver.setDirection('inactive');
-          }
-        } else if (offerOptions.offerToReceiveVideo === true &&
-            !videoTransceiver) {
-          pc.addTransceiver('video');
-        }
-      }
-      return origCreateOffer.apply(pc, arguments);
-    };
-  }
-};
-
-// Expose public methods.
-module.exports = {
-  shimCallbacksAPI: safariShim.shimCallbacksAPI,
-  shimLocalStreamsAPI: safariShim.shimLocalStreamsAPI,
-  shimRemoteStreamsAPI: safariShim.shimRemoteStreamsAPI,
-  shimGetUserMedia: safariShim.shimGetUserMedia,
-  shimRTCIceServerUrls: safariShim.shimRTCIceServerUrls,
-  shimTrackEventTransceiver: safariShim.shimTrackEventTransceiver,
-  shimCreateOfferLegacy: safariShim.shimCreateOfferLegacy
-  // TODO
-  // shimPeerConnection: safariShim.shimPeerConnection
-};
-
-},{"../utils":13}],13:[function(require,module,exports){
-/*
- *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree.
- */
- /* eslint-env node */
-'use strict';
-
-var logDisabled_ = true;
-var deprecationWarnings_ = true;
-
-// Utility methods.
-var utils = {
-  disableLog: function(bool) {
-    if (typeof bool !== 'boolean') {
-      return new Error('Argument type: ' + typeof bool +
-          '. Please use a boolean.');
-    }
-    logDisabled_ = bool;
-    return (bool) ? 'adapter.js logging disabled' :
-        'adapter.js logging enabled';
-  },
-
-  /**
-   * Disable or enable deprecation warnings
-   * @param {!boolean} bool set to true to disable warnings.
-   */
-  disableWarnings: function(bool) {
-    if (typeof bool !== 'boolean') {
-      return new Error('Argument type: ' + typeof bool +
-          '. Please use a boolean.');
-    }
-    deprecationWarnings_ = !bool;
-    return 'adapter.js deprecation warnings ' + (bool ? 'disabled' : 'enabled');
-  },
-
-  log: function() {
-    if (typeof window === 'object') {
-      if (logDisabled_) {
-        return;
-      }
-      if (typeof console !== 'undefined' && typeof console.log === 'function') {
-        console.log.apply(console, arguments);
-      }
-    }
-  },
-
-  /**
-   * Shows a deprecation warning suggesting the modern and spec-compatible API.
-   */
-  deprecated: function(oldMethod, newMethod) {
-    if (!deprecationWarnings_) {
-      return;
-    }
-    console.warn(oldMethod + ' is deprecated, please use ' + newMethod +
-        ' instead.');
-  },
-
-  /**
-   * Extract browser version out of the provided user agent string.
-   *
-   * @param {!string} uastring userAgent string.
-   * @param {!string} expr Regular expression used as match criteria.
-   * @param {!number} pos position in the version string to be returned.
-   * @return {!number} browser version.
-   */
-  extractVersion: function(uastring, expr, pos) {
-    var match = uastring.match(expr);
-    return match && match.length >= pos && parseInt(match[pos], 10);
-  },
-
-  /**
-   * Browser detector.
-   *
-   * @return {object} result containing browser and version
-   *     properties.
-   */
-  detectBrowser: function(window) {
-    var navigator = window && window.navigator;
-
-    // Returned result object.
-    var result = {};
-    result.browser = null;
-    result.version = null;
-
-    // Fail early if it's not a browser
-    if (typeof window === 'undefined' || !window.navigator) {
-      result.browser = 'Not a browser.';
-      return result;
-    }
-
-    // Firefox.
-    if (navigator.mozGetUserMedia) {
-      result.browser = 'firefox';
-      result.version = this.extractVersion(navigator.userAgent,
-          /Firefox\/(\d+)\./, 1);
-    } else if (navigator.webkitGetUserMedia) {
-      // Chrome, Chromium, Webview, Opera, all use the chrome shim for now
-      if (window.webkitRTCPeerConnection) {
-        result.browser = 'chrome';
-        result.version = this.extractVersion(navigator.userAgent,
-          /Chrom(e|ium)\/(\d+)\./, 2);
-      } else { // Safari (in an unpublished version) or unknown webkit-based.
-        if (navigator.userAgent.match(/Version\/(\d+).(\d+)/)) {
-          result.browser = 'safari';
-          result.version = this.extractVersion(navigator.userAgent,
-            /AppleWebKit\/(\d+)\./, 1);
-        } else { // unknown webkit-based browser.
-          result.browser = 'Unsupported webkit-based browser ' +
-              'with GUM support but no WebRTC support.';
-          return result;
-        }
-      }
-    } else if (navigator.mediaDevices &&
-        navigator.userAgent.match(/Edge\/(\d+).(\d+)$/)) { // Edge.
-      result.browser = 'edge';
-      result.version = this.extractVersion(navigator.userAgent,
-          /Edge\/(\d+).(\d+)$/, 2);
-    } else if (navigator.mediaDevices &&
-        navigator.userAgent.match(/AppleWebKit\/(\d+)\./)) {
-        // Safari, with webkitGetUserMedia removed.
-      result.browser = 'safari';
-      result.version = this.extractVersion(navigator.userAgent,
-          /AppleWebKit\/(\d+)\./, 1);
-    } else { // Default fallthrough: not supported.
-      result.browser = 'Not a supported browser.';
-      return result;
-    }
-
-    return result;
-  },
-
-};
-
-// Export.
-module.exports = {
-  log: utils.log,
-  deprecated: utils.deprecated,
-  disableLog: utils.disableLog,
-  disableWarnings: utils.disableWarnings,
-  extractVersion: utils.extractVersion,
-  shimCreateObjectURL: utils.shimCreateObjectURL,
-  detectBrowser: utils.detectBrowser.bind(utils)
-};
-
-},{}]},{},[3])(3)
-});
\ No newline at end of file
diff --git a/web/index.html b/web/index.html
index 7e2b59a..d3f6a4b 100644
--- a/web/index.html
+++ b/web/index.html
@@ -3,19 +3,30 @@
     <link rel="stylesheet" href="style.css">
     </head>
     <body>
-      <p>
-        This is a demo for the web build of Rusty Microphone using
-        Emscripten. It requires a browser that supports WebAssembly
-        and the Web Audio API. There may still be some rough edges
-        that need to be refined. If it does not appear to be working,
-        please make sure that you are using the latest version of your
-        web browser, since these technologies are still relatively
-        new.
-      </p>
-
       <h1>Rusty Microphone</h1>
-      <div id="rusty-microphone">
-        
+      <div id="loading">
+        Loading...
+      </div>
+      <div id="browser-support-error" class="error" style="display:none;">
+        <p>
+          It looks like something has gone wrong while loading. The
+          most likely reason for this is that this app doesn't support
+          your web browser.
+        </p>
+
+        <p>
+          I test with the latest version of Firefox, but it should
+          also work with recent versions of Chrome, Microsoft Edge,
+          Safari and Opera. If you're running one of these browsers,
+          please make sure you've updated to the latest version.
+        </p>
+      </div>
+      <div id="unexpected-error" class="error" style="display:none;">
+        <p>
+          An unexpected error has occurred. Please try again later.
+        </p>
+      </div>
+      <div id="rusty-microphone" style="display:none;">
         <p>The current note being played is <span id="pitch-label">unknown</span></p>
         <div id="pitch-indicator-bar-container">
           <div id="pitch-indicator-bar"></div>
@@ -27,10 +38,9 @@
 
         <canvas id="oscilloscope" width="320" height="300"></canvas>
 
-        <p>The current framerate is <span id="frame-rate">_</span>FPS</p>
+        <p>The current framerate is <span id="frame-rate">0</span>FPS</p>
       </div>
 
-      <script src="adapter.js"></script>
       <script src="main.js"></script>
       <script src="rusty_microphone.js"></script>
     </body>
diff --git a/web/main.js b/web/main.js
index ff78eb4..1d65e7a 100644
--- a/web/main.js
+++ b/web/main.js
@@ -1,9 +1,35 @@
-// This is read and used by `site.js`
+// This is read and used by `rusty_microphone.js`
 var Module = {
     noInitialRun: true,
     noExitRuntime: true,
-    onRuntimeInitialized: main
+    onRuntimeInitialized: main,
+    onAbort: onAbort
 };
+checkBrowserSupport();
+
+function onAbort(reason) {
+    document.getElementById('loading').setAttribute('style', 'display:none');
+    document.getElementById('rusty-microphone').setAttribute('style', 'display:none');
+    document.getElementById('unexpected-error').removeAttribute('style');
+}
+
+function supportsWasm() {
+    return typeof WebAssembly === 'object';
+}
+
+function supportsUserMedia() {
+    return typeof navigator === 'object' &&
+        typeof navigator.mediaDevices === 'object' &&
+        typeof navigator.mediaDevices.getUserMedia === 'function' &&
+        typeof AudioContext === "function";
+}
+
+function checkBrowserSupport() {    
+    if (!supportsWasm() || !supportsUserMedia()) {
+        document.getElementById('loading').setAttribute('style', 'display:none');
+        document.getElementById('browser-support-error').removeAttribute('style');
+    }    
+}
 
 /**
  * Puts at javascript float array onto the heap and provides a pointer
@@ -133,6 +159,11 @@ function initView() {
     var lastTimestamp = 0;
     var timestampMod = 0;
 
+    document.getElementById('loading').setAttribute('style', 'display: none');
+    document.getElementById('browser-support-error').setAttribute('style', 'display: none');
+    document.getElementById('unexpected-error').setAttribute('style', 'display: none');
+    document.getElementById('rusty-microphone').removeAttribute('style');
+
     function draw(signal, timestamp, pitch, error) {
         updateFramerate(timestamp);
         updatePitchIndicators(pitch, error);
@@ -207,9 +238,13 @@ function initView() {
 
 
 function main() {
+    if (!supportsUserMedia()) {
+        return;
+    }
+    
     navigator.mediaDevices.getUserMedia({ audio: true })
         .then(function(stream) {
-            var context = new window.AudioContext();
+            var context = new AudioContext();
             var input = context.createMediaStreamSource(stream);
             var analyser = context.createAnalyser();
             analyser.fftSize = 512;
@@ -227,7 +262,7 @@ function main() {
             window.requestAnimationFrame(analyserNodeCallback);
         })
         .catch(function(err) {
-            console.error('Could not open the microphone stream');
-            console.error(err);
+            document.getElementById('loading').setAttribute('style', 'display:none');
+            document.getElementById('unexpected-error').removeAttribute('style');
         });
 }
diff --git a/web/style.css b/web/style.css
index f704d6f..57bfbe3 100644
--- a/web/style.css
+++ b/web/style.css
@@ -9,7 +9,9 @@
     width: calc(100% - 2px);
     height: 30px;
     position: relative;
-    background: rgb(200, 200, 200);
+    background: #C8C8C8;
+    border-right: 2px solid #C8C8C8;
+    box-sizing: content-box;
 }
 #pitch-indicator-bar {
     height: 100%;
@@ -37,3 +39,8 @@
     background: red;
     float: left;
 }
+
+.error {
+    border: 1px solid red;
+    padding: 10px;
+}