Update media::AudioClock API to take time since writing into account.

media/filters/audio_clock.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_FILTERS_AUDIO_CLOCK_H_
 #define MEDIA_FILTERS_AUDIO_CLOCK_H_
 
 #include <deque>
 
 #include "base/time/time.h"
@@ skipping 17 matching lines @@
                   int delay_frames,
                   float playback_rate,
                   base::TimeDelta timestamp);
 
   // |frames| amount of silence was written.
   // |delay_frames| is the current amount of hardware delay.
   void WroteSilence(int frames, int delay_frames);
 
   // Calculates the current media timestamp taking silence and changes in
   // playback rate into account.
-  base::TimeDelta CurrentMediaTimestamp() const;
+  //
+  // Clients can provide |time_since_writing| to simulate the passage of time

[DaleCurtis, 2014/07/15 18:13:15]

Hmm, I don't quite understand how you're going to use this.  I understand what
the unittest is trying to do, but I don't follow how callers will know "time
since writing."  Can you elaborate?

+  // since last writing audio to get a more accurate current media timestamp.
+  base::TimeDelta CurrentMediaTimestamp(
+      base::TimeDelta time_since_writing) const;
 
   // Returns the last endpoint timestamp provided to WroteAudio().
   base::TimeDelta last_endpoint_timestamp() const {
     return last_endpoint_timestamp_;
   }
 
  private:
   void TrimBufferedAudioToMatchDelay(int delay_frames);
   void PushBufferedAudio(int frames,
                          float playback_rate,
@@ skipping 18 matching lines @@
   };
 
   std::deque<BufferedAudio> buffered_audio_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioClock);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_AUDIO_CLOCK_H_