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

content/common/media/media_stream_options.cc

 // 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.
 
 #include "content/common/media/media_stream_options.h"
 
 #include "base/logging.h"
 
 namespace content {
 
 const char kMediaStreamSource[] = "chromeMediaSource";
 const char kMediaStreamSourceId[] = "chromeMediaSourceId";
 const char kMediaStreamSourceInfoId[] = "sourceId";
 const char kMediaStreamSourceTab[] = "tab";
 const char kMediaStreamSourceScreen[] = "screen";
 const char kMediaStreamSourceDesktop[] = "desktop";
 const char kMediaStreamSourceSystem[] = "system";
 const char kMediaStreamRenderToAssociatedSink[] =
     "chromeRenderToAssociatedSink";
+// The prefix of this constant is 'goog' to match with other getUserMedia
+// constraints for audio.
+const char kMediaStreamAudioDucking[] = "googDucking";
 
 namespace {
 
 bool GetFirstConstraintByName(const StreamOptions::Constraints& constraints,
                               const std::string& name,
                               std::string* value) {
   for (StreamOptions::Constraints::const_iterator it = constraints.begin();
       it != constraints.end(); ++it ) {
     if (it->name == name) {
       *value = it->value;
@@ skipping 88 matching lines @@
 }
 
 // static
 bool StreamDeviceInfo::IsEqual(const StreamDeviceInfo& first,
                                const StreamDeviceInfo& second) {
   return first.device.IsEqual(second.device) &&
       first.session_id == second.session_id;
 }
 
 }  // namespace content