Revert of Moving MediaStreamSignaling logic into PeerConnection.

talk/app/webrtc/mediastreamsignaling.cc

Index: talk/app/webrtc/mediastreamsignaling.cc
diff --git a/talk/app/webrtc/mediastreamsignaling.cc b/talk/app/webrtc/mediastreamsignaling.cc
index b405273902248a8060ef32422d2943496f9c20fa..c12471c778b8d321a3b8b66a5e6ac3f72d5f0b18 100644
--- a/talk/app/webrtc/mediastreamsignaling.cc
+++ b/talk/app/webrtc/mediastreamsignaling.cc
@@ -27,4 +27,1000 @@
 
 #include "talk/app/webrtc/mediastreamsignaling.h"
 
-// TODO(deadbeef): Remove this file once Chrome build files don't reference it.
+#include <vector>
+
+#include "talk/app/webrtc/audiotrack.h"
+#include "talk/app/webrtc/mediaconstraintsinterface.h"
+#include "talk/app/webrtc/mediastreamproxy.h"
+#include "talk/app/webrtc/mediastreamtrackproxy.h"
+#include "talk/app/webrtc/remoteaudiosource.h"
+#include "talk/app/webrtc/remotevideocapturer.h"
+#include "talk/app/webrtc/sctputils.h"
+#include "talk/app/webrtc/videosource.h"
+#include "talk/app/webrtc/videotrack.h"
+#include "talk/media/sctp/sctpdataengine.h"
+#include "webrtc/base/bytebuffer.h"
+#include "webrtc/base/stringutils.h"
+
+static const char kDefaultStreamLabel[] = "default";
+static const char kDefaultAudioTrackLabel[] = "defaulta0";
+static const char kDefaultVideoTrackLabel[] = "defaultv0";
+
+namespace webrtc {
+
+using rtc::scoped_ptr;
+using rtc::scoped_refptr;
+
+static bool ParseConstraintsForAnswer(
+    const MediaConstraintsInterface* constraints,
+    cricket::MediaSessionOptions* options) {
+  bool value = false;
+  size_t mandatory_constraints_satisfied = 0;
+
+  // kOfferToReceiveAudio defaults to true according to spec.
+  if (!FindConstraint(constraints,
+                      MediaConstraintsInterface::kOfferToReceiveAudio,
+                      &value, &mandatory_constraints_satisfied) || value) {
+    options->recv_audio = true;
+  }
+
+  // kOfferToReceiveVideo defaults to false according to spec. But
+  // if it is an answer and video is offered, we should still accept video
+  // per default.
+  value = false;
+  if (!FindConstraint(constraints,
+                      MediaConstraintsInterface::kOfferToReceiveVideo,
+                      &value, &mandatory_constraints_satisfied) || value) {
+    options->recv_video = true;
+  }
+
+  if (FindConstraint(constraints,
+                     MediaConstraintsInterface::kVoiceActivityDetection,
+                     &value, &mandatory_constraints_satisfied)) {
+    options->vad_enabled = value;
+  }
+
+  if (FindConstraint(constraints,
+                     MediaConstraintsInterface::kUseRtpMux,
+                     &value, &mandatory_constraints_satisfied)) {
+    options->bundle_enabled = value;
+  } else {
+    // kUseRtpMux defaults to true according to spec.
+    options->bundle_enabled = true;
+  }
+  if (FindConstraint(constraints,
+                     MediaConstraintsInterface::kIceRestart,
+                     &value, &mandatory_constraints_satisfied)) {
+    options->transport_options.ice_restart = value;
+  } else {
+    // kIceRestart defaults to false according to spec.
+    options->transport_options.ice_restart = false;
+  }
+
+  if (!constraints) {
+    return true;
+  }
+  return mandatory_constraints_satisfied == constraints->GetMandatory().size();
+}
+
+// Returns true if if at least one media content is present and
+// |options.bundle_enabled| is true.
+// Bundle will be enabled  by default if at least one media content is present
+// and the constraint kUseRtpMux has not disabled bundle.
+static bool EvaluateNeedForBundle(const cricket::MediaSessionOptions& options) {
+  return options.bundle_enabled &&
+      (options.has_audio() || options.has_video() || options.has_data());
+}
+
+static bool MediaContentDirectionHasSend(cricket::MediaContentDirection dir) {
+  return dir == cricket::MD_SENDONLY || dir == cricket::MD_SENDRECV;
+}
+
+static bool IsValidOfferToReceiveMedia(int value) {
+  typedef PeerConnectionInterface::RTCOfferAnswerOptions Options;
+  return (value >= Options::kUndefined) &&
+      (value <= Options::kMaxOfferToReceiveMedia);
+}
+
+// Add the stream and RTP data channel info to |session_options|.
+static void SetStreams(
+    cricket::MediaSessionOptions* session_options,
+    rtc::scoped_refptr<StreamCollection> streams,
+    const MediaStreamSignaling::RtpDataChannels& rtp_data_channels) {
+  session_options->streams.clear();
+  if (streams != NULL) {
+    for (size_t i = 0; i < streams->count(); ++i) {
+      MediaStreamInterface* stream = streams->at(i);
+
+      AudioTrackVector audio_tracks(stream->GetAudioTracks());
+
+      // For each audio track in the stream, add it to the MediaSessionOptions.
+      for (size_t j = 0; j < audio_tracks.size(); ++j) {
+        scoped_refptr<MediaStreamTrackInterface> track(audio_tracks[j]);
+        session_options->AddSendStream(
+            cricket::MEDIA_TYPE_AUDIO, track->id(), stream->label());
+      }
+
+      VideoTrackVector video_tracks(stream->GetVideoTracks());
+
+      // For each video track in the stream, add it to the MediaSessionOptions.
+      for (size_t j = 0; j < video_tracks.size(); ++j) {
+        scoped_refptr<MediaStreamTrackInterface> track(video_tracks[j]);
+        session_options->AddSendStream(
+            cricket::MEDIA_TYPE_VIDEO, track->id(), stream->label());
+      }
+    }
+  }
+
+  // Check for data channels.
+  MediaStreamSignaling::RtpDataChannels::const_iterator data_channel_it =
+      rtp_data_channels.begin();
+  for (; data_channel_it != rtp_data_channels.end(); ++data_channel_it) {
+    const DataChannel* channel = data_channel_it->second;
+    if (channel->state() == DataChannel::kConnecting ||
+        channel->state() == DataChannel::kOpen) {
+      // |streamid| and |sync_label| are both set to the DataChannel label
+      // here so they can be signaled the same way as MediaStreams and Tracks.
+      // For MediaStreams, the sync_label is the MediaStream label and the
+      // track label is the same as |streamid|.
+      const std::string& streamid = channel->label();
+      const std::string& sync_label = channel->label();
+      session_options->AddSendStream(
+          cricket::MEDIA_TYPE_DATA, streamid, sync_label);
+    }
+  }
+}
+
+// Factory class for creating remote MediaStreams and MediaStreamTracks.
+class RemoteMediaStreamFactory {
+ public:
+  explicit RemoteMediaStreamFactory(rtc::Thread* signaling_thread,
+                                    cricket::ChannelManager* channel_manager)
+      : signaling_thread_(signaling_thread),
+        channel_manager_(channel_manager) {
+  }
+
+  rtc::scoped_refptr<MediaStreamInterface> CreateMediaStream(
+      const std::string& stream_label) {
+    return MediaStreamProxy::Create(
+        signaling_thread_, MediaStream::Create(stream_label));
+  }
+
+  AudioTrackInterface* AddAudioTrack(webrtc::MediaStreamInterface* stream,
+                                     const std::string& track_id) {
+    return AddTrack<AudioTrackInterface, AudioTrack, AudioTrackProxy>(
+        stream, track_id, RemoteAudioSource::Create().get());
+  }
+
+  VideoTrackInterface* AddVideoTrack(webrtc::MediaStreamInterface* stream,
+                                     const std::string& track_id) {
+    return AddTrack<VideoTrackInterface, VideoTrack, VideoTrackProxy>(
+        stream, track_id, VideoSource::Create(channel_manager_,
+                                              new RemoteVideoCapturer(),
+                                              NULL).get());
+  }
+
+ private:
+  template <typename TI, typename T, typename TP, typename S>
+  TI* AddTrack(MediaStreamInterface* stream, const std::string& track_id,
+               S* source) {
+    rtc::scoped_refptr<TI> track(
+        TP::Create(signaling_thread_, T::Create(track_id, source)));
+    track->set_state(webrtc::MediaStreamTrackInterface::kLive);
+    if (stream->AddTrack(track)) {
+      return track;
+    }
+    return NULL;
+  }
+
+  rtc::Thread* signaling_thread_;
+  cricket::ChannelManager* channel_manager_;
+};
+
+MediaStreamSignaling::MediaStreamSignaling(
+    rtc::Thread* signaling_thread,
+    MediaStreamSignalingObserver* stream_observer,
+    cricket::ChannelManager* channel_manager)
+    : signaling_thread_(signaling_thread),
+      data_channel_factory_(NULL),
+      stream_observer_(stream_observer),
+      local_streams_(StreamCollection::Create()),
+      remote_streams_(StreamCollection::Create()),
+      remote_stream_factory_(new RemoteMediaStreamFactory(signaling_thread,
+                                                          channel_manager)),
+      last_allocated_sctp_even_sid_(-2),
+      last_allocated_sctp_odd_sid_(-1) {
+}
+
+MediaStreamSignaling::~MediaStreamSignaling() {
+}
+
+void MediaStreamSignaling::TearDown() {
+  OnAudioChannelClose();
+  OnVideoChannelClose();
+  OnDataChannelClose();
+}
+
+bool MediaStreamSignaling::IsSctpSidAvailable(int sid) const {
+  if (sid < 0 || sid > static_cast<int>(cricket::kMaxSctpSid))
+    return false;
+
+  return FindDataChannelBySid(sid) < 0;
+}
+
+// Gets the first unused odd/even id based on the DTLS role. If |role| is
+// SSL_CLIENT, the allocated id starts from 0 and takes even numbers; otherwise,
+// the id starts from 1 and takes odd numbers. Returns false if no id can be
+// allocated.
+bool MediaStreamSignaling::AllocateSctpSid(rtc::SSLRole role, int* sid) {
+  int& last_id = (role == rtc::SSL_CLIENT) ?
+      last_allocated_sctp_even_sid_ : last_allocated_sctp_odd_sid_;
+
+  do {
+    last_id += 2;
+  } while (last_id <= static_cast<int>(cricket::kMaxSctpSid) &&
+           !IsSctpSidAvailable(last_id));
+
+  if (last_id > static_cast<int>(cricket::kMaxSctpSid)) {
+    return false;
+  }
+
+  *sid = last_id;
+  return true;
+}
+
+bool MediaStreamSignaling::HasDataChannels() const {
+  return !rtp_data_channels_.empty() || !sctp_data_channels_.empty();
+}
+
+bool MediaStreamSignaling::AddDataChannel(DataChannel* data_channel) {
+  ASSERT(data_channel != NULL);
+  if (data_channel->data_channel_type() == cricket::DCT_RTP) {
+    if (rtp_data_channels_.find(data_channel->label()) !=
+        rtp_data_channels_.end()) {
+      LOG(LS_ERROR) << "DataChannel with label " << data_channel->label()
+                    << " already exists.";
+      return false;
+    }
+    rtp_data_channels_[data_channel->label()] = data_channel;
+  } else {
+    ASSERT(data_channel->data_channel_type() == cricket::DCT_SCTP);
+    sctp_data_channels_.push_back(data_channel);
+  }
+  return true;
+}
+
+bool MediaStreamSignaling::AddDataChannelFromOpenMessage(
+    const cricket::ReceiveDataParams& params,
+    const rtc::Buffer& payload) {
+  if (!data_channel_factory_) {
+    LOG(LS_WARNING) << "Remote peer requested a DataChannel but DataChannels "
+                    << "are not supported.";
+    return false;
+  }
+
+  std::string label;
+  InternalDataChannelInit config;
+  config.id = params.ssrc;
+  if (!ParseDataChannelOpenMessage(payload, &label, &config)) {
+    LOG(LS_WARNING) << "Failed to parse the OPEN message for sid "
+                    << params.ssrc;
+    return false;
+  }
+  config.open_handshake_role = InternalDataChannelInit::kAcker;
+
+  scoped_refptr<DataChannel> channel(
+      data_channel_factory_->CreateDataChannel(label, &config));
+  if (!channel.get()) {
+    LOG(LS_ERROR) << "Failed to create DataChannel from the OPEN message.";
+    return false;
+  }
+
+  stream_observer_->OnAddDataChannel(channel);
+  return true;
+}
+
+void MediaStreamSignaling::RemoveSctpDataChannel(int sid) {
+  ASSERT(sid >= 0);
+  for (SctpDataChannels::iterator iter = sctp_data_channels_.begin();
+       iter != sctp_data_channels_.end();
+       ++iter) {
+    if ((*iter)->id() == sid) {
+      sctp_data_channels_.erase(iter);
+
+      if (rtc::IsEven(sid) && sid <= last_allocated_sctp_even_sid_) {
+        last_allocated_sctp_even_sid_ = sid - 2;
+      } else if (rtc::IsOdd(sid) && sid <= last_allocated_sctp_odd_sid_) {
+        last_allocated_sctp_odd_sid_ = sid - 2;
+      }
+      return;
+    }
+  }
+}
+
+bool MediaStreamSignaling::AddLocalStream(MediaStreamInterface* local_stream) {
+  if (local_streams_->find(local_stream->label()) != NULL) {
+    LOG(LS_WARNING) << "MediaStream with label " << local_stream->label()
+                    << "already exist.";
+    return false;
+  }
+  local_streams_->AddStream(local_stream);
+
+  // Find tracks that has already been configured in SDP. This can occur if a
+  // local session description that contains the MSID of these tracks is set
+  // before AddLocalStream is called. It can also occur if the local session
+  // description is not changed and RemoveLocalStream
+  // is called and later AddLocalStream is called again with the same stream.
+  AudioTrackVector audio_tracks = local_stream->GetAudioTracks();
+  for (AudioTrackVector::const_iterator it = audio_tracks.begin();
+       it != audio_tracks.end(); ++it) {
+    const TrackInfo* track_info = FindTrackInfo(local_audio_tracks_,
+                                                local_stream->label(),
+                                                (*it)->id());
+    if (track_info) {
+      OnLocalTrackSeen(track_info->stream_label, track_info->track_id,
+                       track_info->ssrc, cricket::MEDIA_TYPE_AUDIO);
+    }
+  }
+
+  VideoTrackVector video_tracks = local_stream->GetVideoTracks();
+  for (VideoTrackVector::const_iterator it = video_tracks.begin();
+       it != video_tracks.end(); ++it) {
+    const TrackInfo* track_info = FindTrackInfo(local_video_tracks_,
+                                                local_stream->label(),
+                                                (*it)->id());
+    if (track_info) {
+      OnLocalTrackSeen(track_info->stream_label, track_info->track_id,
+                       track_info->ssrc, cricket::MEDIA_TYPE_VIDEO);
+    }
+  }
+  return true;
+}
+
+void MediaStreamSignaling::RemoveLocalStream(
+    MediaStreamInterface* local_stream) {
+  AudioTrackVector audio_tracks = local_stream->GetAudioTracks();
+  for (AudioTrackVector::const_iterator it = audio_tracks.begin();
+       it != audio_tracks.end(); ++it) {
+    const TrackInfo* track_info = FindTrackInfo(local_audio_tracks_,
+                                                local_stream->label(),
+                                                (*it)->id());
+    if (track_info) {
+      stream_observer_->OnRemoveLocalAudioTrack(local_stream, *it,
+                                                track_info->ssrc);
+    }
+  }
+  VideoTrackVector video_tracks = local_stream->GetVideoTracks();
+  for (VideoTrackVector::const_iterator it = video_tracks.begin();
+       it != video_tracks.end(); ++it) {
+    const TrackInfo* track_info = FindTrackInfo(local_video_tracks_,
+                                                local_stream->label(),
+                                                (*it)->id());
+    if (track_info) {
+      stream_observer_->OnRemoveLocalVideoTrack(local_stream, *it);
+    }
+  }
+
+  local_streams_->RemoveStream(local_stream);
+  stream_observer_->OnRemoveLocalStream(local_stream);
+}
+
+bool MediaStreamSignaling::GetOptionsForOffer(
+    const PeerConnectionInterface::RTCOfferAnswerOptions& rtc_options,
+    cricket::MediaSessionOptions* session_options) {
+  typedef PeerConnectionInterface::RTCOfferAnswerOptions RTCOfferAnswerOptions;
+  if (!IsValidOfferToReceiveMedia(rtc_options.offer_to_receive_audio) ||
+      !IsValidOfferToReceiveMedia(rtc_options.offer_to_receive_video)) {
+    return false;
+  }
+
+  SetStreams(session_options, local_streams_, rtp_data_channels_);
+
+  // According to the spec, offer to receive audio/video if the constraint is
+  // not set and there are send streams.
+  if (rtc_options.offer_to_receive_audio == RTCOfferAnswerOptions::kUndefined) {
+    session_options->recv_audio =
+        session_options->HasSendMediaStream(cricket::MEDIA_TYPE_AUDIO);
+  } else {
+    session_options->recv_audio = (rtc_options.offer_to_receive_audio > 0);
+  }
+  if (rtc_options.offer_to_receive_video == RTCOfferAnswerOptions::kUndefined) {
+    session_options->recv_video =
+        session_options->HasSendMediaStream(cricket::MEDIA_TYPE_VIDEO);
+  } else {
+    session_options->recv_video = (rtc_options.offer_to_receive_video > 0);
+  }
+
+  session_options->vad_enabled = rtc_options.voice_activity_detection;
+  session_options->transport_options.ice_restart = rtc_options.ice_restart;
+  session_options->bundle_enabled = rtc_options.use_rtp_mux;
+
+  session_options->bundle_enabled = EvaluateNeedForBundle(*session_options);
+  return true;
+}
+
+bool MediaStreamSignaling::GetOptionsForAnswer(
+    const MediaConstraintsInterface* constraints,
+    cricket::MediaSessionOptions* options) {
+  SetStreams(options, local_streams_, rtp_data_channels_);
+
+  options->recv_audio = false;
+  options->recv_video = false;
+  if (!ParseConstraintsForAnswer(constraints, options)) {
+    return false;
+  }
+  options->bundle_enabled = EvaluateNeedForBundle(*options);
+  return true;
+}
+
+// Updates or creates remote MediaStream objects given a
+// remote SessionDesription.
+// If the remote SessionDesription contains new remote MediaStreams
+// the observer OnAddStream method is called. If a remote MediaStream is missing
+// from the remote SessionDescription OnRemoveStream is called.
+void MediaStreamSignaling::OnRemoteDescriptionChanged(
+    const SessionDescriptionInterface* desc) {
+  const cricket::SessionDescription* remote_desc = desc->description();
+  rtc::scoped_refptr<StreamCollection> new_streams(
+      StreamCollection::Create());
+
+  // Find all audio rtp streams and create corresponding remote AudioTracks
+  // and MediaStreams.
+  const cricket::ContentInfo* audio_content = GetFirstAudioContent(remote_desc);
+  if (audio_content) {
+    const cricket::AudioContentDescription* desc =
+        static_cast<const cricket::AudioContentDescription*>(
+            audio_content->description);
+    UpdateRemoteStreamsList(desc->streams(), desc->type(), new_streams);
+    remote_info_.default_audio_track_needed =
+        MediaContentDirectionHasSend(desc->direction()) &&
+            desc->streams().empty();
+  }
+
+  // Find all video rtp streams and create corresponding remote VideoTracks
+  // and MediaStreams.
+  const cricket::ContentInfo* video_content = GetFirstVideoContent(remote_desc);
+  if (video_content) {
+    const cricket::VideoContentDescription* desc =
+        static_cast<const cricket::VideoContentDescription*>(
+            video_content->description);
+    UpdateRemoteStreamsList(desc->streams(), desc->type(), new_streams);
+    remote_info_.default_video_track_needed =
+        MediaContentDirectionHasSend(desc->direction()) &&
+            desc->streams().empty();
+  }
+
+  // Update the DataChannels with the information from the remote peer.
+  const cricket::ContentInfo* data_content = GetFirstDataContent(remote_desc);
+  if (data_content) {
+    const cricket::DataContentDescription* data_desc =
+        static_cast<const cricket::DataContentDescription*>(
+            data_content->description);
+    if (rtc::starts_with(
+            data_desc->protocol().data(), cricket::kMediaProtocolRtpPrefix)) {
+      UpdateRemoteRtpDataChannels(data_desc->streams());
+    }
+  }
+
+  // Iterate new_streams and notify the observer about new MediaStreams.
+  for (size_t i = 0; i < new_streams->count(); ++i) {
+    MediaStreamInterface* new_stream = new_streams->at(i);
+    stream_observer_->OnAddRemoteStream(new_stream);
+  }
+
+  // Find removed MediaStreams.
+  if (remote_info_.IsDefaultMediaStreamNeeded() &&
+      remote_streams_->find(kDefaultStreamLabel) != NULL) {
+    // The default media stream already exists. No need to do anything.
+  } else {
+    UpdateEndedRemoteMediaStreams();
+    remote_info_.msid_supported |= remote_streams_->count() > 0;
+  }
+  MaybeCreateDefaultStream();
+}
+
+void MediaStreamSignaling::OnLocalDescriptionChanged(
+    const SessionDescriptionInterface* desc) {
+  const cricket::ContentInfo* audio_content =
+      GetFirstAudioContent(desc->description());
+  if (audio_content) {
+    if (audio_content->rejected) {
+      RejectRemoteTracks(cricket::MEDIA_TYPE_AUDIO);
+    }
+    const cricket::AudioContentDescription* audio_desc =
+        static_cast<const cricket::AudioContentDescription*>(
+            audio_content->description);
+    UpdateLocalTracks(audio_desc->streams(), audio_desc->type());
+  }
+
+  const cricket::ContentInfo* video_content =
+      GetFirstVideoContent(desc->description());
+  if (video_content) {
+    if (video_content->rejected) {
+      RejectRemoteTracks(cricket::MEDIA_TYPE_VIDEO);
+    }
+    const cricket::VideoContentDescription* video_desc =
+        static_cast<const cricket::VideoContentDescription*>(
+            video_content->description);
+    UpdateLocalTracks(video_desc->streams(), video_desc->type());
+  }
+
+  const cricket::ContentInfo* data_content =
+      GetFirstDataContent(desc->description());
+  if (data_content) {
+    const cricket::DataContentDescription* data_desc =
+        static_cast<const cricket::DataContentDescription*>(
+            data_content->description);
+    if (rtc::starts_with(
+            data_desc->protocol().data(), cricket::kMediaProtocolRtpPrefix)) {
+      UpdateLocalRtpDataChannels(data_desc->streams());
+    }
+  }
+}
+
+void MediaStreamSignaling::OnAudioChannelClose() {
+  RejectRemoteTracks(cricket::MEDIA_TYPE_AUDIO);
+}
+
+void MediaStreamSignaling::OnVideoChannelClose() {
+  RejectRemoteTracks(cricket::MEDIA_TYPE_VIDEO);
+}
+
+void MediaStreamSignaling::OnDataChannelClose() {
+  // Use a temporary copy of the RTP/SCTP DataChannel list because the
+  // DataChannel may callback to us and try to modify the list.
+  RtpDataChannels temp_rtp_dcs;
+  temp_rtp_dcs.swap(rtp_data_channels_);
+  RtpDataChannels::iterator it1 = temp_rtp_dcs.begin();
+  for (; it1 != temp_rtp_dcs.end(); ++it1) {
+    it1->second->OnDataEngineClose();
+  }
+
+  SctpDataChannels temp_sctp_dcs;
+  temp_sctp_dcs.swap(sctp_data_channels_);
+  SctpDataChannels::iterator it2 = temp_sctp_dcs.begin();
+  for (; it2 != temp_sctp_dcs.end(); ++it2) {
+    (*it2)->OnDataEngineClose();
+  }
+}
+
+void MediaStreamSignaling::UpdateRemoteStreamsList(
+    const cricket::StreamParamsVec& streams,
+    cricket::MediaType media_type,
+    StreamCollection* new_streams) {
+  TrackInfos* current_tracks = GetRemoteTracks(media_type);
+
+  // Find removed tracks. Ie tracks where the track id or ssrc don't match the
+  // new StreamParam.
+  TrackInfos::iterator track_it = current_tracks->begin();
+  while (track_it != current_tracks->end()) {
+    const TrackInfo& info = *track_it;
+    const cricket::StreamParams* params =
+        cricket::GetStreamBySsrc(streams, info.ssrc);
+    if (!params || params->id != info.track_id) {
+      OnRemoteTrackRemoved(info.stream_label, info.track_id, media_type);
+      track_it = current_tracks->erase(track_it);
+    } else {
+      ++track_it;
+    }
+  }
+
+  // Find new and active tracks.
+  for (cricket::StreamParamsVec::const_iterator it = streams.begin();
+       it != streams.end(); ++it) {
+    // The sync_label is the MediaStream label and the |stream.id| is the
+    // track id.
+    const std::string& stream_label = it->sync_label;
+    const std::string& track_id = it->id;
+    uint32_t ssrc = it->first_ssrc();
+
+    rtc::scoped_refptr<MediaStreamInterface> stream =
+        remote_streams_->find(stream_label);
+    if (!stream) {
+      // This is a new MediaStream. Create a new remote MediaStream.
+      stream = remote_stream_factory_->CreateMediaStream(stream_label);
+      remote_streams_->AddStream(stream);
+      new_streams->AddStream(stream);
+    }
+
+    const TrackInfo* track_info = FindTrackInfo(*current_tracks, stream_label,
+                                                track_id);
+    if (!track_info) {
+      current_tracks->push_back(TrackInfo(stream_label, track_id, ssrc));
+      OnRemoteTrackSeen(stream_label, track_id, it->first_ssrc(), media_type);
+    }
+  }
+}
+
+void MediaStreamSignaling::OnRemoteTrackSeen(const std::string& stream_label,
+                                             const std::string& track_id,
+                                             uint32_t ssrc,
+                                             cricket::MediaType media_type) {
+  MediaStreamInterface* stream = remote_streams_->find(stream_label);
+
+  if (media_type == cricket::MEDIA_TYPE_AUDIO) {
+    AudioTrackInterface* audio_track =
+        remote_stream_factory_->AddAudioTrack(stream, track_id);
+    stream_observer_->OnAddRemoteAudioTrack(stream, audio_track, ssrc);
+  } else if (media_type == cricket::MEDIA_TYPE_VIDEO) {
+    VideoTrackInterface* video_track =
+        remote_stream_factory_->AddVideoTrack(stream, track_id);
+    stream_observer_->OnAddRemoteVideoTrack(stream, video_track, ssrc);
+  } else {
+    ASSERT(false && "Invalid media type");
+  }
+}
+
+void MediaStreamSignaling::OnRemoteTrackRemoved(
+    const std::string& stream_label,
+    const std::string& track_id,
+    cricket::MediaType media_type) {
+  MediaStreamInterface* stream = remote_streams_->find(stream_label);
+
+  if (media_type == cricket::MEDIA_TYPE_AUDIO) {
+    rtc::scoped_refptr<AudioTrackInterface> audio_track =
+        stream->FindAudioTrack(track_id);
+    if (audio_track) {
+      audio_track->set_state(webrtc::MediaStreamTrackInterface::kEnded);
+      stream->RemoveTrack(audio_track);
+      stream_observer_->OnRemoveRemoteAudioTrack(stream, audio_track);
+    }
+  } else if (media_type == cricket::MEDIA_TYPE_VIDEO) {
+    rtc::scoped_refptr<VideoTrackInterface> video_track =
+        stream->FindVideoTrack(track_id);
+    if (video_track) {
+      video_track->set_state(webrtc::MediaStreamTrackInterface::kEnded);
+      stream->RemoveTrack(video_track);
+      stream_observer_->OnRemoveRemoteVideoTrack(stream, video_track);
+    }
+  } else {
+    ASSERT(false && "Invalid media type");
+  }
+}
+
+void MediaStreamSignaling::RejectRemoteTracks(cricket::MediaType media_type) {
+  TrackInfos* current_tracks = GetRemoteTracks(media_type);
+  for (TrackInfos::iterator track_it = current_tracks->begin();
+       track_it != current_tracks->end(); ++track_it) {
+    const TrackInfo& info = *track_it;
+    MediaStreamInterface* stream = remote_streams_->find(info.stream_label);
+    if (media_type == cricket::MEDIA_TYPE_AUDIO) {
+      AudioTrackInterface* track = stream->FindAudioTrack(info.track_id);
+      // There's no guarantee the track is still available, e.g. the track may
+      // have been removed from the stream by javascript.
+      if (track) {
+        track->set_state(webrtc::MediaStreamTrackInterface::kEnded);
+      }
+    }
+    if (media_type == cricket::MEDIA_TYPE_VIDEO) {
+      VideoTrackInterface* track = stream->FindVideoTrack(info.track_id);
+      // There's no guarantee the track is still available, e.g. the track may
+      // have been removed from the stream by javascript.
+      if (track) {
+        track->set_state(webrtc::MediaStreamTrackInterface::kEnded);
+      }
+    }
+  }
+}
+
+void MediaStreamSignaling::UpdateEndedRemoteMediaStreams() {
+  std::vector<scoped_refptr<MediaStreamInterface> > streams_to_remove;
+  for (size_t i = 0; i < remote_streams_->count(); ++i) {
+    MediaStreamInterface*stream = remote_streams_->at(i);
+    if (stream->GetAudioTracks().empty() && stream->GetVideoTracks().empty()) {
+      streams_to_remove.push_back(stream);
+    }
+  }
+
+  std::vector<scoped_refptr<MediaStreamInterface> >::const_iterator it;
+  for (it = streams_to_remove.begin(); it != streams_to_remove.end(); ++it) {
+    remote_streams_->RemoveStream(*it);
+    stream_observer_->OnRemoveRemoteStream(*it);
+  }
+}
+
+void MediaStreamSignaling::MaybeCreateDefaultStream() {
+  if (!remote_info_.IsDefaultMediaStreamNeeded())
+    return;
+
+  bool default_created = false;
+
+  scoped_refptr<MediaStreamInterface> default_remote_stream =
+      remote_streams_->find(kDefaultStreamLabel);
+  if (default_remote_stream == NULL) {
+    default_created = true;
+    default_remote_stream =
+        remote_stream_factory_->CreateMediaStream(kDefaultStreamLabel);
+    remote_streams_->AddStream(default_remote_stream);
+  }
+  if (remote_info_.default_audio_track_needed &&
+      default_remote_stream->GetAudioTracks().size() == 0) {
+    remote_audio_tracks_.push_back(TrackInfo(kDefaultStreamLabel,
+                                             kDefaultAudioTrackLabel, 0));
+
+    OnRemoteTrackSeen(kDefaultStreamLabel, kDefaultAudioTrackLabel, 0,
+                      cricket::MEDIA_TYPE_AUDIO);
+  }
+  if (remote_info_.default_video_track_needed &&
+      default_remote_stream->GetVideoTracks().size() == 0) {
+    remote_video_tracks_.push_back(TrackInfo(kDefaultStreamLabel,
+                                             kDefaultVideoTrackLabel, 0));
+    OnRemoteTrackSeen(kDefaultStreamLabel, kDefaultVideoTrackLabel, 0,
+                      cricket::MEDIA_TYPE_VIDEO);
+  }
+  if (default_created) {
+    stream_observer_->OnAddRemoteStream(default_remote_stream);
+  }
+}
+
+MediaStreamSignaling::TrackInfos* MediaStreamSignaling::GetRemoteTracks(
+    cricket::MediaType type) {
+  if (type == cricket::MEDIA_TYPE_AUDIO)
+    return &remote_audio_tracks_;
+  else if (type == cricket::MEDIA_TYPE_VIDEO)
+    return &remote_video_tracks_;
+  ASSERT(false && "Unknown MediaType");
+  return NULL;
+}
+
+MediaStreamSignaling::TrackInfos* MediaStreamSignaling::GetLocalTracks(
+    cricket::MediaType media_type) {
+  ASSERT(media_type == cricket::MEDIA_TYPE_AUDIO ||
+         media_type == cricket::MEDIA_TYPE_VIDEO);
+
+  return (media_type == cricket::MEDIA_TYPE_AUDIO) ?
+      &local_audio_tracks_ : &local_video_tracks_;
+}
+
+void MediaStreamSignaling::UpdateLocalTracks(
+    const std::vector<cricket::StreamParams>& streams,
+    cricket::MediaType media_type) {
+  TrackInfos* current_tracks = GetLocalTracks(media_type);
+
+  // Find removed tracks. Ie tracks where the track id, stream label or ssrc
+  // don't match the new StreamParam.
+  TrackInfos::iterator track_it = current_tracks->begin();
+  while (track_it != current_tracks->end()) {
+    const TrackInfo& info = *track_it;
+    const cricket::StreamParams* params =
+        cricket::GetStreamBySsrc(streams, info.ssrc);
+    if (!params || params->id != info.track_id ||
+        params->sync_label != info.stream_label) {
+      OnLocalTrackRemoved(info.stream_label, info.track_id, info.ssrc,
+                          media_type);
+      track_it = current_tracks->erase(track_it);
+    } else {
+      ++track_it;
+    }
+  }
+
+  // Find new and active tracks.
+  for (cricket::StreamParamsVec::const_iterator it = streams.begin();
+       it != streams.end(); ++it) {
+    // The sync_label is the MediaStream label and the |stream.id| is the
+    // track id.
+    const std::string& stream_label = it->sync_label;
+    const std::string& track_id = it->id;
+    uint32_t ssrc = it->first_ssrc();
+    const TrackInfo* track_info = FindTrackInfo(*current_tracks,
+                                                stream_label,
+                                                track_id);
+    if (!track_info) {
+      current_tracks->push_back(TrackInfo(stream_label, track_id, ssrc));
+      OnLocalTrackSeen(stream_label, track_id, it->first_ssrc(), media_type);
+    }
+  }
+}
+
+void MediaStreamSignaling::OnLocalTrackSeen(const std::string& stream_label,
+                                            const std::string& track_id,
+                                            uint32_t ssrc,
+                                            cricket::MediaType media_type) {
+  MediaStreamInterface* stream = local_streams_->find(stream_label);
+  if (!stream) {
+    LOG(LS_WARNING) << "An unknown local MediaStream with label "
+                    << stream_label <<  " has been configured.";
+    return;
+  }
+
+  if (media_type == cricket::MEDIA_TYPE_AUDIO) {
+    AudioTrackInterface* audio_track = stream->FindAudioTrack(track_id);
+    if (!audio_track) {
+      LOG(LS_WARNING) << "An unknown local AudioTrack with id , "
+                      << track_id <<  " has been configured.";
+      return;
+    }
+    stream_observer_->OnAddLocalAudioTrack(stream, audio_track, ssrc);
+  } else if (media_type == cricket::MEDIA_TYPE_VIDEO) {
+    VideoTrackInterface* video_track = stream->FindVideoTrack(track_id);
+    if (!video_track) {
+      LOG(LS_WARNING) << "An unknown local VideoTrack with id , "
+                      << track_id <<  " has been configured.";
+      return;
+    }
+    stream_observer_->OnAddLocalVideoTrack(stream, video_track, ssrc);
+  } else {
+    ASSERT(false && "Invalid media type");
+  }
+}
+
+void MediaStreamSignaling::OnLocalTrackRemoved(const std::string& stream_label,
+                                               const std::string& track_id,
+                                               uint32_t ssrc,
+                                               cricket::MediaType media_type) {
+  MediaStreamInterface* stream = local_streams_->find(stream_label);
+  if (!stream) {
+    // This is the normal case. Ie RemoveLocalStream has been called and the
+    // SessionDescriptions has been renegotiated.
+    return;
+  }
+  // A track has been removed from the SessionDescription but the MediaStream
+  // is still associated with MediaStreamSignaling. This only occurs if the SDP
+  // doesn't match with the calls to AddLocalStream and RemoveLocalStream.
+
+  if (media_type == cricket::MEDIA_TYPE_AUDIO) {
+    AudioTrackInterface* audio_track = stream->FindAudioTrack(track_id);
+    if (!audio_track) {
+      return;
+    }
+    stream_observer_->OnRemoveLocalAudioTrack(stream, audio_track, ssrc);
+  } else if (media_type == cricket::MEDIA_TYPE_VIDEO) {
+    VideoTrackInterface* video_track = stream->FindVideoTrack(track_id);
+    if (!video_track) {
+      return;
+    }
+    stream_observer_->OnRemoveLocalVideoTrack(stream, video_track);
+  } else {
+    ASSERT(false && "Invalid media type.");
+  }
+}
+
+void MediaStreamSignaling::UpdateLocalRtpDataChannels(
+    const cricket::StreamParamsVec& streams) {
+  std::vector<std::string> existing_channels;
+
+  // Find new and active data channels.
+  for (cricket::StreamParamsVec::const_iterator it =streams.begin();
+       it != streams.end(); ++it) {
+    // |it->sync_label| is actually the data channel label. The reason is that
+    // we use the same naming of data channels as we do for
+    // MediaStreams and Tracks.
+    // For MediaStreams, the sync_label is the MediaStream label and the
+    // track label is the same as |streamid|.
+    const std::string& channel_label = it->sync_label;
+    RtpDataChannels::iterator data_channel_it =
+        rtp_data_channels_.find(channel_label);
+    if (!VERIFY(data_channel_it != rtp_data_channels_.end())) {
+      continue;
+    }
+    // Set the SSRC the data channel should use for sending.
+    data_channel_it->second->SetSendSsrc(it->first_ssrc());
+    existing_channels.push_back(data_channel_it->first);
+  }
+
+  UpdateClosingDataChannels(existing_channels, true);
+}
+
+void MediaStreamSignaling::UpdateRemoteRtpDataChannels(
+    const cricket::StreamParamsVec& streams) {
+  std::vector<std::string> existing_channels;
+
+  // Find new and active data channels.
+  for (cricket::StreamParamsVec::const_iterator it = streams.begin();
+       it != streams.end(); ++it) {
+    // The data channel label is either the mslabel or the SSRC if the mslabel
+    // does not exist. Ex a=ssrc:444330170 mslabel:test1.
+    std::string label = it->sync_label.empty() ?
+        rtc::ToString(it->first_ssrc()) : it->sync_label;
+    RtpDataChannels::iterator data_channel_it =
+        rtp_data_channels_.find(label);
+    if (data_channel_it == rtp_data_channels_.end()) {
+      // This is a new data channel.
+      CreateRemoteDataChannel(label, it->first_ssrc());
+    } else {
+      data_channel_it->second->SetReceiveSsrc(it->first_ssrc());
+    }
+    existing_channels.push_back(label);
+  }
+
+  UpdateClosingDataChannels(existing_channels, false);
+}
+
+void MediaStreamSignaling::UpdateClosingDataChannels(
+    const std::vector<std::string>& active_channels, bool is_local_update) {
+  RtpDataChannels::iterator it = rtp_data_channels_.begin();
+  while (it != rtp_data_channels_.end()) {
+    DataChannel* data_channel = it->second;
+    if (std::find(active_channels.begin(), active_channels.end(),
+                  data_channel->label()) != active_channels.end()) {
+      ++it;
+      continue;
+    }
+
+    if (is_local_update)
+      data_channel->SetSendSsrc(0);
+    else
+      data_channel->RemotePeerRequestClose();
+
+    if (data_channel->state() == DataChannel::kClosed) {
+      rtp_data_channels_.erase(it);
+      it = rtp_data_channels_.begin();
+    } else {
+      ++it;
+    }
+  }
+}
+
+void MediaStreamSignaling::CreateRemoteDataChannel(const std::string& label,
+                                                   uint32_t remote_ssrc) {
+  if (!data_channel_factory_) {
+    LOG(LS_WARNING) << "Remote peer requested a DataChannel but DataChannels "
+                    << "are not supported.";
+    return;
+  }
+  scoped_refptr<DataChannel> channel(
+      data_channel_factory_->CreateDataChannel(label, NULL));
+  if (!channel.get()) {
+    LOG(LS_WARNING) << "Remote peer requested a DataChannel but"
+                    << "CreateDataChannel failed.";
+    return;
+  }
+  channel->SetReceiveSsrc(remote_ssrc);
+  stream_observer_->OnAddDataChannel(channel);
+}
+
+void MediaStreamSignaling::OnDataTransportCreatedForSctp() {
+  SctpDataChannels::iterator it = sctp_data_channels_.begin();
+  for (; it != sctp_data_channels_.end(); ++it) {
+    (*it)->OnTransportChannelCreated();
+  }
+}
+
+void MediaStreamSignaling::OnDtlsRoleReadyForSctp(rtc::SSLRole role) {
+  SctpDataChannels::iterator it = sctp_data_channels_.begin();
+  for (; it != sctp_data_channels_.end(); ++it) {
+    if ((*it)->id() < 0) {
+      int sid;
+      if (!AllocateSctpSid(role, &sid)) {
+        LOG(LS_ERROR) << "Failed to allocate SCTP sid.";
+        continue;
+      }
+      (*it)->SetSctpSid(sid);
+    }
+  }
+}
+
+void MediaStreamSignaling::OnRemoteSctpDataChannelClosed(uint32_t sid) {
+  int index = FindDataChannelBySid(sid);
+  if (index < 0) {
+    LOG(LS_WARNING) << "Unexpected sid " << sid
+                    << " of the remotely closed DataChannel.";
+    return;
+  }
+  sctp_data_channels_[index]->Close();
+}
+
+const MediaStreamSignaling::TrackInfo*
+MediaStreamSignaling::FindTrackInfo(
+    const MediaStreamSignaling::TrackInfos& infos,
+    const std::string& stream_label,
+    const std::string track_id) const {
+
+  for (TrackInfos::const_iterator it = infos.begin();
+      it != infos.end(); ++it) {
+    if (it->stream_label == stream_label && it->track_id == track_id)
+      return &*it;
+  }
+  return NULL;
+}
+
+int MediaStreamSignaling::FindDataChannelBySid(int sid) const {
+  for (size_t i = 0; i < sctp_data_channels_.size(); ++i) {
+    if (sctp_data_channels_[i]->id() == sid) {
+      return static_cast<int>(i);
+    }
+  }
+  return -1;
+}
+
+}  // namespace webrtc