Remove unused RenderIO() interface.

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 b2f4ba0a90201b6420106fde54faa8ebcf7437bf..fa1ee84c250a10e16eb0db310b38a31cd555c65c 100644
--- a/media/base/audio_renderer_sink.h
+++ b/media/base/audio_renderer_sink.h
@@ -28,11 +28,6 @@ class AudioRendererSink
     // number of frames filled.
     virtual int Render(AudioBus* dest, int audio_delay_milliseconds) = 0;
 
-    // Synchronized audio I/O - see InitializeIO() below.
-    virtual void RenderIO(AudioBus* source,
-                          AudioBus* dest,
-                          int audio_delay_milliseconds) {}
-
     // Signals an error has occurred.
     virtual void OnRenderError() = 0;