Add support for audio input mute detection on all platforms

media/audio/audio_io.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_AUDIO_IO_H_
 #define MEDIA_AUDIO_AUDIO_IO_H_
 
 #include "base/basictypes.h"
 #include "media/base/audio_bus.h"
 
@@ skipping 146 matching lines @@
   virtual void SetVolume(double volume) = 0;
 
   // Returns the microphone analog volume, with range [0, max_volume] inclusive.
   virtual double GetVolume() = 0;
 
   // Sets the Automatic Gain Control (AGC) state.
   virtual void SetAutomaticGainControl(bool enabled) = 0;
 
   // Returns the Automatic Gain Control (AGC) state.
   virtual bool GetAutomaticGainControl() = 0;
+
+  // Returns the current muting state for the microphone.
+  virtual bool IsMuted() = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_IO_H_