Refactor AudioRendererMixer to be more generic.

media/base/audio_converter.h

Index: media/base/audio_converter.h
diff --git a/media/base/audio_converter.h b/media/base/audio_converter.h
index 983855bdbfa0c5a97b6ade7b7c28397641509b05..a1f901694cb7d8d836cedd6b88635373f94cff05 100644
--- a/media/base/audio_converter.h
+++ b/media/base/audio_converter.h
@@ -74,8 +74,10 @@ class MEDIA_EXPORT AudioConverter {
   ~AudioConverter();
 
   // Converts audio from all inputs into the |dest|.  |dest| must be sized for
-  // data matching the output AudioParameters provided during construction.
+  // data matching the output AudioParameters provided during construction.  If
+  // an |initial_delay| is specified, it will be propagated to each input.
   void Convert(AudioBus* dest);
+  void ConvertWithDelay(const base::TimeDelta& initial_delay, AudioBus* dest);
 
   // Adds or removes an input from the converter.  RemoveInput() will call
   // Reset() if no inputs remain after the specified input is removed.
@@ -120,6 +122,7 @@ class MEDIA_EXPORT AudioConverter {
   // Used to calculate buffer delay information for InputCallbacks.
   base::TimeDelta input_frame_duration_;
   base::TimeDelta output_frame_duration_;
+  base::TimeDelta initial_delay_;
   int resampler_frame_delay_;
 
   // Number of channels of input audio data.  Set during construction via the