Fix incorrect opus seek preroll and flaky pre-skip removal.

media/audio/clockless_audio_sink.h

Index: media/audio/clockless_audio_sink.h
diff --git a/media/audio/clockless_audio_sink.h b/media/audio/clockless_audio_sink.h
index 1e7e43e9cec1d2833f0b2628d80b4afc6100d582..96745a51ed72ffd91864e5007464c3950c056353 100644
--- a/media/audio/clockless_audio_sink.h
+++ b/media/audio/clockless_audio_sink.h
@@ -40,6 +40,12 @@ class MEDIA_EXPORT ClocklessAudioSink
   // Returns the time taken to consume all the audio.
   base::TimeDelta render_time() { return playback_time_; }
 
+  // Enables audio frame hashing.  Must be called prior to Initialize().
+  void StartAudioHashForTesting();
+
+  // Returns the hash of all audio frames seen since construction.
+  std::string GetAudioHashForTesting();
+
  protected:
   ~ClocklessAudioSink() override;
 
@@ -47,6 +53,7 @@ class MEDIA_EXPORT ClocklessAudioSink
   scoped_ptr<ClocklessAudioSinkThread> thread_;
   bool initialized_;
   bool playing_;
+  bool hashing_;
 
   // Time taken in last set of Render() calls.
   base::TimeDelta playback_time_;