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

content/public/browser/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_PUBLIC_BROWSER_MEDIA_OBSERVER_H_
 #define CONTENT_PUBLIC_BROWSER_MEDIA_OBSERVER_H_
 
 #include "content/public/browser/media_request_state.h"
 #include "content/public/common/media_stream_request.h"
 
 namespace media {
 struct MediaLogEvent;
 }
 
 namespace content {
 
 // An embedder may implement MediaObserver and return it from
 // ContentBrowserClient to receive callbacks as media events occur.
 class MediaObserver {
  public:
   // Called when an audio stream is deleted.
   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",
   // "closed", or "error".
   virtual void OnSetAudioStreamStatus(void* host, int stream_id,
                                       const std::string& status) = 0;
 
   // Called when the volume of an audio stream is set.
   virtual void OnSetAudioStreamVolume(void* host, int stream_id,
                                       double volume) = 0;
@@ skipping 29 matching lines @@
       const MediaStreamDevice& device,
       MediaRequestState state) = 0;
 
  protected:
   virtual ~MediaObserver() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_MEDIA_OBSERVER_H_