Implement mapping blink track id to demuxer streams

media/filters/media_source_state.h

Index: media/filters/media_source_state.h
diff --git a/media/filters/media_source_state.h b/media/filters/media_source_state.h
index 3eb5e5491de1621a6a17b33f02472a07e643b9a0..5fdb20ff4d0131988c3661e441f43fa7c8b6c922 100644
--- a/media/filters/media_source_state.h
+++ b/media/filters/media_source_state.h
@@ -20,12 +20,13 @@ using base::TimeDelta;
 
 class ChunkDemuxerStream;
 class FrameProcessor;
+class MediaTrack;
 
 // Contains state belonging to a source id.
 class MEDIA_EXPORT MediaSourceState {
  public:
   // Callback signature used to create ChunkDemuxerStreams.
-  typedef base::Callback<ChunkDemuxerStream*(DemuxerStream::Type)>
+  typedef base::Callback<ChunkDemuxerStream*(const MediaTrack&)>
       CreateDemuxerStreamCB;
 
   typedef base::Callback<void(ChunkDemuxerStream*, const TextTrackConfig&)>
@@ -190,8 +191,6 @@ class MEDIA_EXPORT MediaSourceState {
   // The object used to parse appended data.
   std::unique_ptr<StreamParser> stream_parser_;
 
-  std::unique_ptr<MediaTracks> media_tracks_;
-
   ChunkDemuxerStream* audio_;  // Not owned by |this|.
   ChunkDemuxerStream* video_;  // Not owned by |this|.