Improve audio/video sync during underflow, reduce underflow frequency.

media/filters/audio_clock.h

Index: media/filters/audio_clock.h
diff --git a/media/filters/audio_clock.h b/media/filters/audio_clock.h
index fe462aba5d5e55e1764ac1a49c24ae89c613f929..f7711f67fd77bb895f5c25923612487379fa5d83 100644
--- a/media/filters/audio_clock.h
+++ b/media/filters/audio_clock.h
@@ -59,6 +59,18 @@ class MEDIA_EXPORT AudioClock {
                   int delay_frames,
                   double playback_rate);
 
+  // If WroteAudio() calls are suspended (i.e. due to playback being paused) the
+  // AudioClock will not properly advance time (even though all data up until
+  // back_timestamp() will playout on the physical device).
+  //
+  // To compensate for this, when calls resume, before the next WroteAudio(),
+  // callers should call CompensateForSuspendedWrites() to advance the clock for
+  // audio which continued playing out while WroteAudio() calls were suspended.
+  //
+  // |delay_frames| must be provided to properly prime the clock to compensate
+  // for a new initial delay.
+  void CompensateForSuspendedWrites(base::TimeDelta elapsed, int delay_frames);
+
   // Returns the bounds of media data currently buffered by the audio hardware,
   // taking silence and changes in playback rate into account. Buffered audio
   // structure and timestamps are updated with every call to WroteAudio().