Support configuring number of audio buffers in MediaStream Pepper API.

ppapi/cpp/media_stream_audio_track.h

Index: ppapi/cpp/media_stream_audio_track.h
diff --git a/ppapi/cpp/media_stream_audio_track.h b/ppapi/cpp/media_stream_audio_track.h
index 19e76b84afc55c82ecbfe9d5c0e928fab2b4687c..680e52b832e804574e8f14349fe672bce062a11b 100644
--- a/ppapi/cpp/media_stream_audio_track.h
+++ b/ppapi/cpp/media_stream_audio_track.h
@@ -56,7 +56,8 @@ class MediaStreamAudioTrack : public Resource {
   /// all input buffers. If all buffers are filled, then samples will be
   /// dropped. The application can detect this by examining the timestamp on
   /// returned buffers. If <code>Configure()</code> is not called, default
-  /// settings will be used.
+  /// settings will be used. Calls to Configure while the plugin holds
+  /// buffers will fail.
   /// Example usage from plugin code:
   /// @code
   /// int32_t attribs[] = {