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

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_MOCK_MEDIA_OBSERVER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_MOCK_MEDIA_OBSERVER_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 16 matching lines @@
                void(int render_process_id, int render_view_id,
                     const MediaStreamDevices& devices));
   MOCK_METHOD1(OnAudioCaptureDevicesChanged,
                void(const MediaStreamDevices& devices));
   MOCK_METHOD1(OnVideoCaptureDevicesChanged,
                  void(const MediaStreamDevices& devices));
   MOCK_METHOD4(OnMediaRequestStateChanged,
                void(int render_process_id, int render_view_id,
                     const MediaStreamDevice& device,
                     const MediaRequestState state));
+  MOCK_METHOD4(OnAudioStreamPlayingChanged,
+               void(int render_process_id,
+                    int render_view_id,
+                    int stream_id,
+                    bool playing));
 };
 
 class MockMediaInternals : public MediaInternals {
  public:
   MockMediaInternals();
   virtual ~MockMediaInternals();
 
   MOCK_METHOD2(OnDeleteAudioStream,
                void(void* host, int stream_id));
   MOCK_METHOD3(OnSetAudioStreamPlaying,
                void(void* host, int stream_id, bool playing));
   MOCK_METHOD3(OnSetAudioStreamStatus,
                void(void* host, int stream_id, const std::string& status));
   MOCK_METHOD3(OnSetAudioStreamVolume,
                void(void* host, int stream_id, double volume));
   MOCK_METHOD2(OnMediaEvent,
                void(int source, const media::MediaLogEvent& event));
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_MOCK_MEDIA_OBSERVER_H_