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 2987b78ecf027c234a749fdb0d18bcd85e58f91f..fc3232d7f05174fc944aa785e7912a9683fca47d 100644
--- a/media/base/audio_converter.h
+++ b/media/base/audio_converter.h
@@ -53,8 +53,10 @@ 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(base::TimeDelta initial_delay, AudioBus* dest);
 
   // Add or remove an input from the converter.
   void AddInput(InputCallback* input);
@@ -96,6 +98,7 @@ 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_;
 
   const int input_channel_count_;