Exposing RtpSenders and RtpReceivers from PeerConnection.

talk/app/webrtc/mediastreamsignaling.h

 /*
  * libjingle
  * Copyright 2012 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
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  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 48 matching lines @@
 
   // Triggered when the remote SessionDescription removes a stream.
   virtual void OnRemoveRemoteStream(MediaStreamInterface* stream) = 0;
 
   // Triggered when the remote SessionDescription has a new data channel.
   virtual void OnAddDataChannel(DataChannelInterface* data_channel) = 0;
 
   // Triggered when the remote SessionDescription has a new audio track.
   virtual void OnAddRemoteAudioTrack(MediaStreamInterface* stream,
                                      AudioTrackInterface* audio_track,
-                                     uint32 ssrc) = 0;
+                                     uint32 ssrc,
+                                     const std::string& mid) = 0;

[pthatcher1, 2015/09/17 04:25:46]

I don't see how MID is even useful here.  I think we should just remove it from
RtpSenders and RtpReceivers for now.  

Here's an idea:  instead of getting the (stream, track, ssrc, mid) from the SDP,
why not instead get (sender_id, ssrc, track), where the sender_id is MSID for
"Plan B" SDP and MID for Unified Plan later?   

We should also add a TODO to change all calls through BaseChannel/MediaChannel
to use "sender_id" instead of SSRC.   Then it would just be (sender_id, track).

We should also add a TODO to change addTrack to put the track on the RtpSender
before the SDP comes in.  Then this callback could just be (sender_id).

[Taylor Brandstetter, 2015/09/23 00:10:45]

It's not useful right now. It's just something I knew we'd need eventually, so I
thought I'd go ahead and add it. But if it's just going to be clutter, I'll go
ahead and remove it.

Also, I'll do the "sender_id" change in the next CL, since it's more relevant
there.

 
   // Triggered when the remote SessionDescription has a new video track.
   virtual void OnAddRemoteVideoTrack(MediaStreamInterface* stream,
                                      VideoTrackInterface* video_track,
-                                     uint32 ssrc) = 0;
+                                     uint32 ssrc,
+                                     const std::string& mid) = 0;
 
   // Triggered when the remote SessionDescription has removed an audio track.
   virtual void OnRemoveRemoteAudioTrack(MediaStreamInterface* stream,
                                         AudioTrackInterface* audio_track)  = 0;
 
   // Triggered when the remote SessionDescription has removed a video track.
   virtual void OnRemoveRemoteVideoTrack(MediaStreamInterface* stream,
                                         VideoTrackInterface* video_track) = 0;
 
   // Triggered when the local SessionDescription has a new audio track.
   virtual void OnAddLocalAudioTrack(MediaStreamInterface* stream,
                                     AudioTrackInterface* audio_track,
-                                    uint32 ssrc) = 0;
+                                    uint32 ssrc,
+                                    const std::string& mid) = 0;
 
   // Triggered when the local SessionDescription has a new video track.
   virtual void OnAddLocalVideoTrack(MediaStreamInterface* stream,
                                     VideoTrackInterface* video_track,
-                                    uint32 ssrc) = 0;
+                                    uint32 ssrc,
+                                    const std::string& mid) = 0;
 
   // Triggered when the local SessionDescription has removed an audio track.
   virtual void OnRemoveLocalAudioTrack(MediaStreamInterface* stream,
                                        AudioTrackInterface* audio_track,
                                        uint32 ssrc) = 0;
 
   // Triggered when the local SessionDescription has removed a video track.
   virtual void OnRemoveLocalVideoTrack(MediaStreamInterface* stream,
                                        VideoTrackInterface* video_track) = 0;
 
@@ skipping 166 matching lines @@
     }
     // True if it has been discovered that the remote peer support MSID.
     bool msid_supported;
     // The remote peer indicates in the session description that audio will be
     // sent but no MSID is given.
     bool default_audio_track_needed;
     // The remote peer indicates in the session description that video will be
     // sent but no MSID is given.
     bool default_video_track_needed;
 
+    // mid strings associated with the empty audio/video content descriptions.
+    std::string default_audio_mid;
+    std::string default_video_mid;
+
     bool IsDefaultMediaStreamNeeded() {
       return !msid_supported && (default_audio_track_needed ||
           default_video_track_needed);
     }
   };
 
   struct TrackInfo {
     TrackInfo() : ssrc(0) {}
     TrackInfo(const std::string& stream_label,
               const std::string track_id,
-              uint32 ssrc)
+              uint32 ssrc,
+              const std::string& mid)
         : stream_label(stream_label),
           track_id(track_id),
-          ssrc(ssrc) {
-    }
+          ssrc(ssrc),
+          mid(mid) {}
     std::string stream_label;
     std::string track_id;
     uint32 ssrc;
+    std::string mid;
   };
   typedef std::vector<TrackInfo> TrackInfos;
 
   // Makes sure a MediaStream Track is created for each StreamParam in
   // |streams|. |media_type| is the type of the |streams| and can be either
   // audio or video.
   // If a new MediaStream is created it is added to |new_streams|.
   void UpdateRemoteStreamsList(
       const std::vector<cricket::StreamParams>& streams,
       cricket::MediaType media_type,
+      const std::string& mid,
       StreamCollection* new_streams);
 
   // Triggered when a remote track has been seen for the first time in a remote
   // session description. It creates a remote MediaStreamTrackInterface
   // implementation and triggers MediaStreamSignaling::OnAddRemoteAudioTrack or
   // MediaStreamSignaling::OnAddRemoteVideoTrack.
   void OnRemoteTrackSeen(const std::string& stream_label,
                          const std::string& track_id,
                          uint32 ssrc,
-                         cricket::MediaType media_type);
+                         cricket::MediaType media_type,
+                         const std::string& mid);
 
   // Triggered when a remote track has been removed from a remote session
   // description. It removes the remote track with id |track_id| from a remote
   // MediaStream and triggers MediaStreamSignaling::OnRemoveRemoteAudioTrack or
   // MediaStreamSignaling::OnRemoveRemoteVideoTrack.
   void OnRemoteTrackRemoved(const std::string& stream_label,
                             const std::string& track_id,
                             cricket::MediaType media_type);
 
   // Set the MediaStreamTrackInterface::TrackState to |kEnded| on all remote
   // tracks of type |media_type|.
   void RejectRemoteTracks(cricket::MediaType media_type);
 
   // Finds remote MediaStreams without any tracks and removes them from
   // |remote_streams_| and notifies the observer that the MediaStream no longer
   // exist.
   void UpdateEndedRemoteMediaStreams();
   void MaybeCreateDefaultStream();
   TrackInfos* GetRemoteTracks(cricket::MediaType type);
 
   // Returns a map of currently negotiated LocalTrackInfo of type |type|.
   TrackInfos* GetLocalTracks(cricket::MediaType type);
   bool FindLocalTrack(const std::string& track_id, cricket::MediaType type);
 
   // Loops through the vector of |streams| and finds added and removed
   // StreamParams since last time this method was called.
   // For each new or removed StreamParam NotifyLocalTrackAdded or
   // NotifyLocalTrackRemoved in invoked.
   void UpdateLocalTracks(const std::vector<cricket::StreamParams>& streams,
-                         cricket::MediaType media_type);
+                         cricket::MediaType media_type,
+                         const std::string& mid);
 
   // Triggered when a local track has been seen for the first time in a local
   // session description.
   // This method triggers MediaStreamSignaling::OnAddLocalAudioTrack or
   // MediaStreamSignaling::OnAddLocalVideoTrack if the rtp streams in the local
   // SessionDescription can be mapped to a MediaStreamTrack in a MediaStream in
   // |local_streams_|
   void OnLocalTrackSeen(const std::string& stream_label,
                         const std::string& track_id,
                         uint32 ssrc,
-                        cricket::MediaType media_type);
+                        cricket::MediaType media_type,
+                        const std::string& mid);
 
   // Triggered when a local track has been removed from a local session
   // description.
   // This method triggers MediaStreamSignaling::OnRemoveLocalAudioTrack or
   // MediaStreamSignaling::OnRemoveLocalVideoTrack if a stream has been removed
   // from the local SessionDescription and the stream can be mapped to a
   // MediaStreamTrack in a MediaStream in |local_streams_|.
   void OnLocalTrackRemoved(const std::string& stream_label,
                            const std::string& track_id,
                            uint32 ssrc,
@@ skipping 29 matching lines @@
   int last_allocated_sctp_even_sid_;
   int last_allocated_sctp_odd_sid_;
 
   RtpDataChannels rtp_data_channels_;
   SctpDataChannels sctp_data_channels_;
 };
 
 }  // namespace webrtc
 
 #endif  // TALK_APP_WEBRTC_MEDIASTREAMSIGNALING_H_