Replace trampolining in FFmpegDemuxer with explicit thread calling convention checks.

media/filters/ffmpeg_demuxer.h

Index: media/filters/ffmpeg_demuxer.h
diff --git a/media/filters/ffmpeg_demuxer.h b/media/filters/ffmpeg_demuxer.h
index 889cc3b0dbb230875a52dfeb586a89dbee8c2a63..34ddbffb259b2cf3e98dbd01b2beb537a18b73c7 100644
--- a/media/filters/ffmpeg_demuxer.h
+++ b/media/filters/ffmpeg_demuxer.h
@@ -154,26 +154,20 @@ class MEDIA_EXPORT FFmpegDemuxer : public Demuxer {
 
   virtual ~FFmpegDemuxer();
 
-  // Carries out initialization on the demuxer thread.
-  void InitializeTask(DemuxerHost* host, const PipelineStatusCB& status_cb);
+  // FFmpeg callbacks during initialization.
   void OnOpenContextDone(const PipelineStatusCB& status_cb, bool result);
   void OnFindStreamInfoDone(const PipelineStatusCB& status_cb, int result);
 
-  // Carries out a seek on the demuxer thread.
-  void SeekTask(base::TimeDelta time, const PipelineStatusCB& cb);
+  // FFmpeg callbacks during seeking.
   void OnSeekFrameDone(const PipelineStatusCB& cb, int result);
 
-  // Carries out demuxing and satisfying stream reads on the demuxer thread.
-  void DemuxTask();
+  // FFmpeg callbacks during reading + helper method to initiate reads.
+  void ReadFrameIfNeeded();
   void OnReadFrameDone(ScopedAVPacket packet, int result);
 
-  // Carries out stopping the demuxer streams on the demuxer thread.
-  void StopTask(const base::Closure& callback);
+  // DataSource callbacks during stopping.
   void OnDataSourceStopped(const base::Closure& callback);
 
-  // Carries out disabling the audio stream on the demuxer thread.
-  void DisableAudioStreamTask();
-
   // Returns true iff any stream has additional capacity. Note that streams can
   // go over capacity depending on how the file is muxed.
   bool StreamsHaveAvailableCapacity();