Change the TimeSource interface to return wallclock time for video.

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 7a764b37c5c3b283ccfc43b27392cdbfe4e8338a..360e632517fbf79621781f4d96f330bc0801d505 100644
--- a/media/base/video_renderer.h
+++ b/media/base/video_renderer.h
@@ -24,8 +24,8 @@ class MEDIA_EXPORT VideoRenderer {
   // Used to paint VideoFrame.
   typedef base::Callback<void(const scoped_refptr<VideoFrame>&)> PaintCB;
 
-  // Used to query the current time or duration of the media.
-  typedef base::Callback<base::TimeDelta()> TimeDeltaCB;
+  // Used to convert a media timestamp into a wall clock timestamp.
+  typedef base::Callback<base::TimeTicks(base::TimeDelta)> WallClockTimeCB;
 
   VideoRenderer();
 
@@ -52,7 +52,8 @@ class MEDIA_EXPORT VideoRenderer {
   //
   // |error_cb| is executed if an error was encountered after initialization.
   //
-  // |get_time_cb| is used to query the current media playback time.
+  // |wall_clock_time_cb| is used to convert media timestamps into wallclock
+  // timestamps.
   //
   // |waiting_for_decryption_key_cb| is executed whenever the key needed to
   // decrypt the stream is not available.
@@ -65,7 +66,7 @@ class MEDIA_EXPORT VideoRenderer {
       const PaintCB& paint_cb,
       const base::Closure& ended_cb,
       const PipelineStatusCB& error_cb,
-      const TimeDeltaCB& get_time_cb,
+      const WallClockTimeCB& wall_clock_time_cb,
       const base::Closure& waiting_for_decryption_key_cb) = 0;
 
   // Discards any video data and stops reading from |stream|, executing