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

content/renderer/media/media_stream_dependency_factory.cc

Index: content/renderer/media/media_stream_dependency_factory.cc
diff --git a/content/renderer/media/media_stream_dependency_factory.cc b/content/renderer/media/media_stream_dependency_factory.cc
index d3357373681f416349d03d44b8babb1275bb98ee..3151d548fb2c6a6da7bd7442ea40d4cf508cfd07 100644
--- a/content/renderer/media/media_stream_dependency_factory.cc
+++ b/content/renderer/media/media_stream_dependency_factory.cc
@@ -58,8 +58,10 @@ struct {
   const char* constraint;
   const media::AudioParameters::PlatformEffectsMask effect;
 } const kConstraintEffectMap[] = {
+  { content::kMediaStreamAudioDucking,
+    media::AudioParameters::DUCKING },
   { webrtc::MediaConstraintsInterface::kEchoCancellation,
-    media::AudioParameters::ECHO_CANCELLER},
+    media::AudioParameters::ECHO_CANCELLER },
 };
 
 class P2PPortAllocatorFactory : public webrtc::PortAllocatorFactoryInterface {