MediaRecorder: support sampling rate adaption in AudioTrackRecorder

content/renderer/media/audio_track_recorder.h

Index: content/renderer/media/audio_track_recorder.h
diff --git a/content/renderer/media/audio_track_recorder.h b/content/renderer/media/audio_track_recorder.h
index 353331cec0f12d3955df45b82d0cdf9cb08ba38c..0883e75279ec550014104e6fe95bc3e6d1f8dc78 100644
--- a/content/renderer/media/audio_track_recorder.h
+++ b/content/renderer/media/audio_track_recorder.h
@@ -46,17 +46,12 @@ class CONTENT_EXPORT AudioTrackRecorder
               base::TimeTicks capture_time) override;
 
  private:
-  friend class AudioTrackRecorderTest;
   class AudioParameters;
 
   // Forward declaration of nested class for handling encoding.
   // See the implementation file for details.
   class AudioEncoder;
 
-  // Returns the Opus buffer duration in milliseconds, or zero if none will work
-  // for the given |sample_rate|.
-  static int GetOpusBufferDuration(int sample_rate);
-
   // Used to check that we are destroyed on the same thread we were created on.
   base::ThreadChecker main_render_thread_checker_;