Implement mapping blink track id to demuxer streams

media/filters/chunk_demuxer.h

Index: media/filters/chunk_demuxer.h
diff --git a/media/filters/chunk_demuxer.h b/media/filters/chunk_demuxer.h
index be0f9dbc38be5283202b297eb17167414d6be383..a27222ac3d34d003d3e33d86dd12bebbf21b901c 100644
--- a/media/filters/chunk_demuxer.h
+++ b/media/filters/chunk_demuxer.h
@@ -19,6 +19,7 @@
 #include "media/base/byte_queue.h"
 #include "media/base/demuxer.h"
 #include "media/base/demuxer_stream.h"
+#include "media/base/media_tracks.h"
 #include "media/base/ranges.h"
 #include "media/base/stream_parser.h"
 #include "media/filters/media_source_state.h"
@@ -208,6 +209,15 @@ class MEDIA_EXPORT ChunkDemuxer : public Demuxer {
   void SetTracksWatcher(const std::string& id,
                         const MediaTracksUpdatedCB& tracks_updated_cb);
 
+  // Notifies the demuxer that track ids has been assigned to a media tracks.
+  void OnTrackIdsAssigned(const MediaTracks& tracks,
+                          const std::vector<unsigned>& track_ids) override;
+
+  // 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.
+  const DemuxerStream* GetDemuxerStreamByTrackId(
+      unsigned track_id) const override;
+
   // Removed an ID & associated resources that were previously added with
   // AddId().
   void RemoveId(const std::string& id);
@@ -318,10 +328,10 @@ class MEDIA_EXPORT ChunkDemuxer : public Demuxer {
   // MediaSourceState callbacks.
   void OnSourceInitDone(const StreamParser::InitParameters& params);
 
-  // Creates a DemuxerStream for the specified |type|.
-  // Returns a new ChunkDemuxerStream instance if a stream of this type
+  // Creates a DemuxerStream for the specified |media_track|.
+  // Returns a new ChunkDemuxerStream instance if a stream of this track's type
   // has not been created before. Returns NULL otherwise.
-  ChunkDemuxerStream* CreateDemuxerStream(DemuxerStream::Type type);
+  ChunkDemuxerStream* CreateDemuxerStream(const MediaTrack& media_track);
 
   void OnNewTextTrack(ChunkDemuxerStream* text_stream,
                       const TextTrackConfig& config);
@@ -385,6 +395,8 @@ class MEDIA_EXPORT ChunkDemuxer : public Demuxer {
   // Incremented in AddId(), decremented in OnSourceInitDone().
   int pending_source_init_done_count_;
 
+  MediaTracks::TrackIdToDemuxStreamMap track_id_to_demux_stream_;
+
   base::TimeDelta duration_;
 
   // The duration passed to the last SetDuration(). If