Allow muting/unmuting audio through media track API

media/base/media_tracks.h

Index: media/base/media_tracks.h
diff --git a/media/base/media_tracks.h b/media/base/media_tracks.h
index 4e0fbb0fc1f88195ce14cc05d14a424924be4d5d..265d8fe0a0ba0a03475ef64fb4bf4647912400fe 100644
--- a/media/base/media_tracks.h
+++ b/media/base/media_tracks.h
@@ -17,30 +17,39 @@
 namespace media {
 
 class AudioDecoderConfig;
+class DemuxerStream;
 class VideoDecoderConfig;
 
 class MEDIA_EXPORT MediaTracks {
  public:
   typedef std::vector<scoped_ptr<MediaTrack>> MediaTracksCollection;
+  typedef std::map<const MediaTrack*, const DemuxerStream*>
+      TrackToDemuxStreamMap;
 
   MediaTracks();
   ~MediaTracks();
 
   // Callers need to ensure that track id is unique.
-  void AddAudioTrack(const AudioDecoderConfig& config,
-                     const std::string& id,
-                     const std::string& kind,
-                     const std::string& label,
-                     const std::string& language);
+  const MediaTrack* AddAudioTrack(const AudioDecoderConfig& config,
+                                  const std::string& id,
+                                  const std::string& kind,
+                                  const std::string& label,
+                                  const std::string& language);
   // Callers need to ensure that track id is unique.
-  void AddVideoTrack(const VideoDecoderConfig& config,
-                     const std::string& id,
-                     const std::string& kind,
-                     const std::string& label,
-                     const std::string& language);
+  const MediaTrack* AddVideoTrack(const VideoDecoderConfig& config,
+                                  const std::string& id,
+                                  const std::string& kind,
+                                  const std::string& label,
+                                  const std::string& language);
 
   const MediaTracksCollection& tracks() const { return tracks_; }
 
+  const TrackToDemuxStreamMap& track_to_demux_stream_map() const {
+    return track_to_demux_stream_map_;
+  }
+
+  void set_track_to_demux_stream_map(const TrackToDemuxStreamMap& m);
+
   const AudioDecoderConfig& getAudioConfig(const std::string& id) const;
   const VideoDecoderConfig& getVideoConfig(const std::string& id) const;
 
@@ -51,6 +60,7 @@ class MEDIA_EXPORT MediaTracks {
 
  private:
   MediaTracksCollection tracks_;
+  TrackToDemuxStreamMap track_to_demux_stream_map_;
   std::map<std::string, AudioDecoderConfig> audio_configs_;
   std::map<std::string, VideoDecoderConfig> video_configs_;