Turn audio ducking on by default on Windows again.

content/renderer/media/media_stream_dispatcher.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_RENDERER_MEDIA_MEDIA_STREAM_DISPATCHER_H_
 #define CONTENT_RENDERER_MEDIA_MEDIA_STREAM_DISPATCHER_H_
 
 #include <list>
 #include <map>
 #include <string>
@@ skipping 77 matching lines @@
   void CloseDevice(const std::string& label);
 
   // Check if the label is a valid stream.
   virtual bool IsStream(const std::string& label);
   // Get the video session_id given a label. The label identifies a stream.
   // index is the index in the video_device_array of the stream.
   virtual int video_session_id(const std::string& label, int index);
   // Returns an audio session_id given a label and an index.
   virtual int audio_session_id(const std::string& label, int index);
 
+  // Returns true if an audio input stream is currently active that was opened
+  // with audio ducking enabled.  This is information is used when playing out
+  // audio so that rendered audio can be excluded from the ducking operation.
+  bool IsAudioDuckingActive() const;
+
  protected:
   int GetNextIpcIdForTest() { return next_ipc_id_; }
 
  private:
   FRIEND_TEST_ALL_PREFIXES(MediaStreamDispatcherTest, BasicVideoDevice);
   FRIEND_TEST_ALL_PREFIXES(MediaStreamDispatcherTest, TestFailure);
   FRIEND_TEST_ALL_PREFIXES(MediaStreamDispatcherTest, CancelGenerateStream);
+  FRIEND_TEST_ALL_PREFIXES(MediaStreamDispatcherTest, CheckDuckingState);
 
   struct Request;
 
   // Private class for keeping track of opened devices and who have
   // opened it.
   struct Stream;
 
   // RenderViewObserver OVERRIDE.
   virtual bool Send(IPC::Message* message) OVERRIDE;
 
@@ skipping 29 matching lines @@
   // been canceled.
   typedef std::list<Request> RequestList;
   RequestList requests_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaStreamDispatcher);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_DISPATCHER_H_