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 38 matching lines @@
 
  protected:
   virtual ~AudioManagerWin();
 
   virtual AudioParameters GetPreferredOutputStreamParameters(
       const std::string& output_device_id,
       const AudioParameters& input_params) OVERRIDE;
 
  private:
   enum EnumerationType {
-    kUninitializedEnumeration = 0,
     kMMDeviceEnumeration,
     kWaveEnumeration,
   };
 
   // Allow unit test to modify the utilized enumeration API.
   friend class AudioManagerTest;
 
   EnumerationType enumeration_type_;
   EnumerationType enumeration_type() { return enumeration_type_; }
   void SetEnumerationType(EnumerationType type) {
     enumeration_type_ = type;
   }
 
+  inline bool core_audio_supported() const {
+    return enumeration_type_ == kMMDeviceEnumeration;
+  }
+
   // Returns a PCMWaveInAudioInputStream instance or NULL on failure.
   // This method converts MMDevice-style device ID to WaveIn-style device ID if
   // necessary.
   // (Please see device_enumeration_win.h for more info about the two kinds of
   // device IDs.)
   AudioInputStream* CreatePCMWaveInAudioInputStream(
       const AudioParameters& params,
       const std::string& device_id);
 
   // 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_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioManagerWin);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_WIN_AUDIO_MANAGER_WIN_H_