Fix playback rate w/o audio. Remove unused SetPlaybackRate().

media/base/audio_renderer_sink.h

Index: media/base/audio_renderer_sink.h
diff --git a/media/base/audio_renderer_sink.h b/media/base/audio_renderer_sink.h
index 3756daafba118badc3850ab0775be133ca0b85fa..8786fe1826634c890643e386c57a83c934f53171 100644
--- a/media/base/audio_renderer_sink.h
+++ b/media/base/audio_renderer_sink.h
@@ -55,10 +55,6 @@ class AudioRendererSink
   // Resumes playback after calling Pause().
   virtual void Play() = 0;
 
-  // Called to inform the sink of a change in playback rate. Override if
-  // subclass needs the playback rate.
-  virtual void SetPlaybackRate(float rate) {}
-
   // Sets the playback volume, with range [0.0, 1.0] inclusive.
   // Returns |true| on success.
   virtual bool SetVolume(double volume) = 0;