Replace the guts of AudioRendererBase with calls to scaling algorithm.

chrome/renderer/media/audio_renderer_impl.h

Index: chrome/renderer/media/audio_renderer_impl.h
===================================================================
--- chrome/renderer/media/audio_renderer_impl.h	(revision 22189)
+++ chrome/renderer/media/audio_renderer_impl.h	(working copy)
@@ -183,7 +183,6 @@
 
   // Protects:
   // - |stopped_|
-  // - |playback_rate_|
   // - |pending_request_|
   // - |request_timestamp_|
   // - |request_delay_|
@@ -192,9 +191,6 @@
   // A flag that indicates this filter is called to stop.
   bool stopped_;
 
-  // Keeps the current playback rate.
-  float playback_rate_;
-
   // A flag that indicates an outstanding packet request.
   bool pending_request_;