Add a method to tab_utils.h to find out whether a tab is playing audio.

content/browser/renderer_host/media/audio_renderer_host.h

Index: content/browser/renderer_host/media/audio_renderer_host.h
diff --git a/content/browser/renderer_host/media/audio_renderer_host.h b/content/browser/renderer_host/media/audio_renderer_host.h
index 44daef21f836cf0ee8da944de1d83fab60b04799..b7851a7c0a0a3d5ee541e25ad30fa64d0d8080e3 100644
--- a/content/browser/renderer_host/media/audio_renderer_host.h
+++ b/content/browser/renderer_host/media/audio_renderer_host.h
@@ -67,7 +67,8 @@ class CONTENT_EXPORT AudioRendererHost
       public media::AudioOutputController::EventHandler {
  public:
   // Called from UI thread from the owner of this object.
-  AudioRendererHost(media::AudioManager* audio_manager,
+  AudioRendererHost(int render_process_id,
+                    media::AudioManager* audio_manager,
                     MediaObserver* media_observer);
 
   // BrowserMessageFilter implementation.
@@ -164,6 +165,8 @@ class CONTENT_EXPORT AudioRendererHost
 
   media::AudioOutputController* LookupControllerByIdForTesting(int stream_id);
 
+  int render_process_id_;
+
   // A map of stream IDs to audio sources.
   AudioEntryMap audio_entries_;