Adds AudioDevice factory for all audio clients in Chrome

content/renderer/media/audio_message_filter.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.
 //
 // MessageFilter that handles audio messages and delegates them to audio
 // renderers. Created on render thread, AudioMessageFilter is operated on
 // IO thread (secondary thread of render process) it intercepts audio messages
 // and process them on IO thread since these messages are time critical.
 
 #ifndef CONTENT_RENDERER_MEDIA_AUDIO_MESSAGE_FILTER_H_
@@ skipping 21 matching lines @@
     virtual void OnStreamCreated(base::SharedMemoryHandle handle,
                                  base::SyncSocket::Handle socket_handle,
                                  uint32 length) = 0;
 
    protected:
     virtual ~Delegate() {}
   };
 
   AudioMessageFilter();
 
+  // Getter for the one AudioMessageFilter object.
+  static AudioMessageFilter* current();
+
   // Add a delegate to the map and return id of the entry.
   int32 AddDelegate(Delegate* delegate);
 
   // Remove a delegate referenced by |id| from the map.
   void RemoveDelegate(int32 id);
 
   // Sends an IPC message using |channel_|.
   bool Send(IPC::Message* message);
 
   // IPC::ChannelProxy::MessageFilter override. Called on IO thread.
@@ skipping 16 matching lines @@
 #else
                        base::FileDescriptor socket_descriptor,
 #endif
                        uint32 length);
 
 
   // Received when internal state of browser process' audio output device has
   // changed.
   void OnStreamStateChanged(int stream_id, AudioStreamState state);
 
+  // The singleton instance for this filter.
+  // Should only be accessed on the main renderer thread.
+  static AudioMessageFilter* filter_;
+
   // A map of stream ids to delegates.
   IDMap<Delegate> delegates_;
 
   IPC::Channel* channel_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioMessageFilter);
 };
 
 #endif  // CONTENT_RENDERER_MEDIA_AUDIO_MESSAGE_FILTER_H_