Introduce TimeSource notifications to the VideoRenderer.

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 360e632517fbf79621781f4d96f330bc0801d505..8c07036cf4e0b11d321f5a3c8991128e58c08596 100644
--- a/media/base/video_renderer.h
+++ b/media/base/video_renderer.h
@@ -82,6 +82,12 @@ class MEDIA_EXPORT VideoRenderer {
   // Only valid to call after a successful Initialize() or Flush().
   virtual void StartPlayingFrom(base::TimeDelta timestamp) = 0;
 
+  // Called when time starts ticking and the playback rate is greater than 0.
+  virtual void OnTimeProgressing() = 0;
+
+  // Called when time stops ticking or the playback rate is zero.
+  virtual void OnTimeStopped() = 0;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(VideoRenderer);
 };