Add basic support for "googDucking" to getUserMedia on Windows.

media/audio/win/audio_manager_win.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 MEDIA_AUDIO_WIN_AUDIO_MANAGER_WIN_H_
 #define MEDIA_AUDIO_WIN_AUDIO_MANAGER_WIN_H_
 
 #include <string>
 
 #include "media/audio/audio_manager_base.h"
@@ skipping 71 matching lines @@
   // Helper methods for performing expensive initialization tasks on the audio
   // thread instead of on the UI thread which AudioManager is constructed on.
   void InitializeOnAudioThread();
   void ShutdownOnAudioThread();
 
   void GetAudioDeviceNamesImpl(bool input, AudioDeviceNames* device_names);
 
   // Listen for output device changes.
   scoped_ptr<AudioDeviceListenerWin> output_device_listener_;
 
+  // Cached value for whether or not we should use the WASAPI based libraries
+  // or not.
+  const bool core_audio_supported_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioManagerWin);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_WIN_AUDIO_MANAGER_WIN_H_