Allow muting/unmuting audio through media track API

media/base/demuxer.h

Index: media/base/demuxer.h
diff --git a/media/base/demuxer.h b/media/base/demuxer.h
index 027264ba79fb916f0359a983d4f4dc4519ccba80..e2c68ebe4b437be2ce5cb9d877bb71c9c73425fd 100644
--- a/media/base/demuxer.h
+++ b/media/base/demuxer.h
@@ -67,7 +67,7 @@ class MEDIA_EXPORT Demuxer : public DemuxerStreamProvider {
       EncryptedMediaInitDataCB;
 
   // Notifies demuxer clients that media track configuration has been updated
-  // (e.g. the inital stream metadata has been parsed successfully, or a new
+  // (e.g. the initial stream metadata has been parsed successfully, or a new
   // init segment has been parsed successfully in MSE case).
   typedef base::Callback<void(scoped_ptr<MediaTracks>)> MediaTracksUpdatedCB;
 
@@ -134,6 +134,18 @@ class MEDIA_EXPORT Demuxer : public DemuxerStreamProvider {
   // Returns the memory usage in bytes for the demuxer.
   virtual int64_t GetMemoryUsage() const = 0;
 
+  // Notifies the demuxer that blink track ids have been assigned to |tracks|.
+  // The |track_ids| collection must contain blink track ids in the same
+  // sequence as media tracks in |tracks|. The collection sizes must be the
+  // same.
+  virtual void OnTrackIdsAssigned(const MediaTracks& tracks,
+                                  const std::vector<unsigned>& track_ids) = 0;
+
+  // Finds a DemuxerStream corresponding to the given blink |track_id|. Note
+  // that the input track id is blink track id and not bytestream track id.
+  virtual const DemuxerStream* GetDemuxerStreamByTrackId(
+      unsigned track_id) const = 0;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(Demuxer);
 };