Part 1: Plumb render view ID to render host

content/renderer/media/audio_renderer_mixer_manager.h

Index: content/renderer/media/audio_renderer_mixer_manager.h
diff --git a/content/renderer/media/audio_renderer_mixer_manager.h b/content/renderer/media/audio_renderer_mixer_manager.h
index 37f432b46d448ea43884d51e63a4b66c02ef7fbd..5f73508fb359cc287b0d8e38986d48519a1f42c5 100644
--- a/content/renderer/media/audio_renderer_mixer_manager.h
+++ b/content/renderer/media/audio_renderer_mixer_manager.h
@@ -40,14 +40,16 @@ class CONTENT_EXPORT AudioRendererMixerManager {
   // Creates an AudioRendererMixerInput with the proper callbacks necessary to
   // retrieve an AudioRendererMixer instance from AudioRendererMixerManager.
   // Caller must ensure AudioRendererMixerManager outlives the returned input.
-  media::AudioRendererMixerInput* CreateInput();
+  media::AudioRendererMixerInput* CreateInput(int render_view_id);
 
  private:
   friend class AudioRendererMixerManagerTest;
 
   // Returns a mixer instance based on AudioParameters; an existing one if one
   // with the provided AudioParameters exists or a new one if not.
-  media::AudioRendererMixer* GetMixer(const media::AudioParameters& params);
+  media::AudioRendererMixer* GetMixer(
+      int render_view_id,
+      const media::AudioParameters& params);
 
   // Remove a mixer instance given a mixer if the only other reference is held
   // by AudioRendererMixerManager.  Every AudioRendererMixer owner must call