Allow media track switching.

media/renderers/renderer_impl.h

Index: media/renderers/renderer_impl.h
diff --git a/media/renderers/renderer_impl.h b/media/renderers/renderer_impl.h
index f55a7635e22707644c5b818813542d23a49544c0..b8d2fcf87e142ee70d33f5c05839ec0c3577c6a2 100644
--- a/media/renderers/renderer_impl.h
+++ b/media/renderers/renderer_impl.h
@@ -106,8 +106,29 @@ class MEDIA_EXPORT RendererImpl : public Renderer {
   void FlushVideoRenderer();
   void OnVideoRendererFlushDone();
 
-  void RestartAudioRenderer(base::TimeDelta time);
-  void RestartVideoRenderer(base::TimeDelta time);
+  // Restart audio/video renderer playback after a media track switch or after a
+  // media track has been disabled and re-enabled. The |stream| parameter
+  // specifies which stream needs to be restarted. If it's the same as the most
+  // recently playing stream of that type, then the renderer is only restarted.
+  // But if it differs from the most recent stream, then the renderer is
+  // completely reinitialized, i.e. the corresponding DecoderStream is recreated
+  // and decoder is reinitialized too.
+  // The |time| parameter specifies the position on the media timeline where the
+  // playback needs to be restarted. It is necessary for demuxers with
+  // independent streams (e.g. MSE / ChunkDemuxer) to synchronize data reading
+  // between those streams.
+  void RestartAudioRenderer(DemuxerStream* stream, base::TimeDelta time);
+  void RestartVideoRenderer(DemuxerStream* stream, base::TimeDelta time);
+
+  // These callbacks are invoked when the corresponding renderer has been
+  // reinitialized. If the |status| indicates success, then playback of the
+  // |stream| should be resumed from media position specified by |time|.
+  void OnAudioRendererReinitCompleted(DemuxerStream* stream,

[xhwang, 2017/03/27 19:13:53]

nit: OnAudioRendererReinitialized, or OnAudioRendererReinitializeDone to be
consistent with line 99

[servolk, 2017/03/27 22:34:13]

Done.

+                                      base::TimeDelta time,
+                                      PipelineStatus status);
+  void OnVideoRendererReinitCompleted(DemuxerStream* stream,
+                                      base::TimeDelta time,
+                                      PipelineStatus status);
 
   // Callback executed by filters to update statistics.
   void OnStatisticsUpdate(const PipelineStatistics& stats);
@@ -166,6 +187,9 @@ class MEDIA_EXPORT RendererImpl : public Renderer {
   std::unique_ptr<AudioRenderer> audio_renderer_;
   std::unique_ptr<VideoRenderer> video_renderer_;
 
+  DemuxerStream* current_audio_stream_;
+  DemuxerStream* current_video_stream_;
+
   // Renderer-provided time source used to control playback.
   TimeSource* time_source_;
   std::unique_ptr<WallClockTimeSource> wall_clock_time_source_;