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

content/common/media/media_stream_options.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_COMMON_MEDIA_MEDIA_STREAM_OPTIONS_H_
 #define CONTENT_COMMON_MEDIA_MEDIA_STREAM_OPTIONS_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 10 matching lines @@
 CONTENT_EXPORT extern const char kMediaStreamSourceScreen[];
 CONTENT_EXPORT extern const char kMediaStreamSourceDesktop[];
 CONTENT_EXPORT extern const char kMediaStreamSourceSystem[];
 
 // Experimental constraint to do device matching.  When this optional constraint
 // is set, WebRTC audio renderer will render audio from media streams to an
 // output device that belongs to the same hardware as the requested source
 // device belongs to.
 CONTENT_EXPORT extern const char kMediaStreamRenderToAssociatedSink[];
 
+// Controls whether ducking of audio is enabled on platforms that support it.
+CONTENT_EXPORT extern const char kMediaStreamAudioDucking[];
+
 // StreamOptions is a Chromium representation of constraints
 // used in WebUserMediaRequest.
 // It describes properties requested by JS in a request for a new
 // media stream.
 class CONTENT_EXPORT StreamOptions {
  public:
   StreamOptions();
   StreamOptions(bool request_audio, bool request_video);
   ~StreamOptions();
 
@@ skipping 64 matching lines @@
 
   // Id for this capture session. Unique for all sessions of the same type.
   int session_id;
 };
 
 typedef std::vector<StreamDeviceInfo> StreamDeviceInfoArray;
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_MEDIA_MEDIA_STREAM_OPTIONS_H_