Introduce media::TimeSource.

media/base/video_renderer.h

Index: media/base/video_renderer.h
diff --git a/media/base/video_renderer.h b/media/base/video_renderer.h
index 2e36c7f56d1a31b8704c75260d7ad84cc9225950..8d436e4b5374bf609c51e8e2d22063a2dd760a08 100644
--- a/media/base/video_renderer.h
+++ b/media/base/video_renderer.h
@@ -35,8 +35,6 @@ class MEDIA_EXPORT VideoRenderer {
   // |statistics_cb| is executed periodically with video rendering stats, such
   // as dropped frames.
   //
-  // |time_cb| is executed whenever time has advanced by way of video rendering.
-  //
   // |buffering_state_cb| is executed when video rendering has either run out of
   // data or has enough data to continue playback.
   //
@@ -51,7 +49,6 @@ class MEDIA_EXPORT VideoRenderer {
                           bool low_delay,
                           const PipelineStatusCB& init_cb,
                           const StatisticsCB& statistics_cb,
-                          const TimeCB& time_cb,
                           const BufferingStateCB& buffering_state_cb,
                           const base::Closure& ended_cb,
                           const PipelineStatusCB& error_cb,
@@ -66,10 +63,9 @@ class MEDIA_EXPORT VideoRenderer {
   virtual void Flush(const base::Closure& callback) = 0;
 
   // Starts playback by reading from |stream| and decoding and rendering video.
-  // |timestamp| is the media timestamp playback should start rendering from.
   //
   // Only valid to call after a successful Initialize() or Flush().
-  virtual void StartPlayingFrom(base::TimeDelta timestamp) = 0;
+  virtual void StartPlaying() = 0;
 
   // Stop all operations in preparation for being deleted, executing |callback|
   // when complete.