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

content/browser/renderer_host/media/mock_media_observer.h

Index: content/browser/renderer_host/media/mock_media_observer.h
diff --git a/content/browser/renderer_host/media/mock_media_observer.h b/content/browser/renderer_host/media/mock_media_observer.h
index afcc70f9606c3b4d10f11335d92cc3151c0c032b..84f9cfa55088e97a33cb9a5f4be2833f8d6f954d 100644
--- a/content/browser/renderer_host/media/mock_media_observer.h
+++ b/content/browser/renderer_host/media/mock_media_observer.h
@@ -21,8 +21,9 @@ class MockMediaObserver : public MediaObserver {
 
   MOCK_METHOD2(OnDeleteAudioStream,
                void(void* host, int stream_id));
-  MOCK_METHOD3(OnSetAudioStreamPlaying,
-               void(void* host, int stream_id, bool playing));
+  MOCK_METHOD5(OnSetAudioStreamPlaying,
+               void(void* host, int stream_id, int render_process_id,
+                    int render_view_id, bool playing));
   MOCK_METHOD3(OnSetAudioStreamStatus,
                void(void* host, int stream_id, const std::string& status));
   MOCK_METHOD3(OnSetAudioStreamVolume,