Add WebMediaPlayer::timelineOffset() support to WebMediaPlayerImpl.

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 7acdd430ccca06761479d859e8740d063cf50d08..60506521f43f1453a0437bdd98bbde20b7c1be70 100644
--- a/media/filters/ffmpeg_demuxer.h
+++ b/media/filters/ffmpeg_demuxer.h
@@ -154,6 +154,7 @@ class MEDIA_EXPORT FFmpegDemuxer : public Demuxer {
   virtual void OnAudioRendererDisabled() OVERRIDE;
   virtual DemuxerStream* GetStream(DemuxerStream::Type type) OVERRIDE;
   virtual base::TimeDelta GetStartTime() const OVERRIDE;
+  virtual base::Time GetWallclockTimelineOffset() const OVERRIDE;
 
   // Calls |need_key_cb_| with the initialization data encountered in the file.
   void FireNeedKey(const std::string& init_data_type,
@@ -246,6 +247,10 @@ class MEDIA_EXPORT FFmpegDemuxer : public Demuxer {
   // is 0.
   base::TimeDelta start_time_;
 
+  // The wallclock time associated with timestamp 0. Set to a null
+  // time if the file doesn't have an association to wallclock time.
+  base::Time wallclock_timeline_offset_;
+
   // Whether audio has been disabled for this demuxer (in which case this class
   // drops packets destined for AUDIO demuxer streams on the floor).
   bool audio_disabled_;