Unify media track info reporting on a demuxer level

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 1197015e2587111b40e55268e9d4c928dcebb260..e6878f6071ce9efe5ac11232970f01395d60a43a 100644
--- a/media/filters/media_source_state.h
+++ b/media/filters/media_source_state.h
@@ -28,8 +28,6 @@ class MEDIA_EXPORT MediaSourceState {
   typedef base::Callback<ChunkDemuxerStream*(DemuxerStream::Type)>
       CreateDemuxerStreamCB;
 
-  typedef base::Callback<void(const MediaTracks&)> InitSegmentReceivedCB;
-
   typedef base::Callback<void(ChunkDemuxerStream*, const TextTrackConfig&)>
       NewTextTrackCB;
 
@@ -52,14 +50,12 @@ class MEDIA_EXPORT MediaSourceState {
   // error occurred. |*timestamp_offset| is used and possibly updated by the
   // append. |append_window_start| and |append_window_end| correspond to the MSE
   // spec's similarly named source buffer attributes that are used in coded
-  // frame processing. |init_segment_received_cb| is run for each new fully
-  // parsed initialization segment.
+  // frame processing.
   bool Append(const uint8_t* data,
               size_t length,
               TimeDelta append_window_start,
               TimeDelta append_window_end,
-              TimeDelta* timestamp_offset,
-              const InitSegmentReceivedCB& init_segment_received_cb);
+              TimeDelta* timestamp_offset);
 
   // Aborts the current append sequence and resets the parser.
   void ResetParserState(TimeDelta append_window_start,
@@ -117,6 +113,8 @@ class MEDIA_EXPORT MediaSourceState {
       const RangesList& activeRanges,
       bool ended);
 
+  void SetTracksWatcher(const Demuxer::MediaTracksUpdatedCB& tracks_updated_cb);

[wolenetz, 2016/03/05 01:47:43]

nit: document what this means; when it should be called, and when the callback
will be called.

[servolk, 2016/03/05 01:56:19]

Will do, but at this point there are three other CLs that are based on this one.
So to avoid too much rebasing, I'll add a comment in separate CL.

+
  private:
   // Called by the |stream_parser_| when a new initialization segment is
   // encountered.
@@ -195,11 +193,13 @@ class MEDIA_EXPORT MediaSourceState {
   StreamParser::InitCB init_cb_;
 
   // During Append(), OnNewConfigs() will trigger the initialization segment
-  // received algorithm. This callback is only non-NULL during the lifetime of
-  // an Append() call. Note, the MSE spec explicitly disallows this algorithm
+  // received algorithm. Note, the MSE spec explicitly disallows this algorithm
   // during an Abort(), since Abort() is allowed only to emit coded frames, and
-  // only if the parser is PARSING_MEDIA_SEGMENT (not an INIT segment).
-  InitSegmentReceivedCB init_segment_received_cb_;
+  // only if the parser is PARSING_MEDIA_SEGMENT (not an INIT segment). So we
+  // also have a flag here that indicates if Append is in progress and we can
+  // invoke this callback.
+  Demuxer::MediaTracksUpdatedCB init_segment_received_cb_;
+  bool append_in_progress_ = false;

[wolenetz, 2016/03/05 01:47:43]

this flag and associated comment and usage seem unnecessary. the previous
comment was there simply because the value of the member callback variable could
only be trusted during an append. so long as we only call it during
append-related processing, we need no such flag.

[servolk, 2016/03/05 01:56:19]

Done.

 
   // Indicates that timestampOffset should be updated automatically during
   // OnNewBuffers() based on the earliest end timestamp of the buffers provided.