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

content/public/browser/media_observer.h

Index: content/public/browser/media_observer.h
diff --git a/content/public/browser/media_observer.h b/content/public/browser/media_observer.h
index cfb066710a0ef3043ba01e45af8d2c572cc3afd3..0a47d8c3e6c2a5edb21ec24996155f1057b357c2 100644
--- a/content/public/browser/media_observer.h
+++ b/content/public/browser/media_observer.h
@@ -22,7 +22,10 @@ class MediaObserver {
   virtual void OnDeleteAudioStream(void* host, int stream_id) = 0;
 
   // Called when an audio stream is set to playing or paused.
-  virtual void OnSetAudioStreamPlaying(void* host, int stream_id,
+  virtual void OnSetAudioStreamPlaying(void* host,
+                                       int stream_id,
+                                       int render_process_id,
+                                       int render_view_id,
                                        bool playing) = 0;
 
   // Called when the status of an audio stream is set to "created", "flushed",