Add support for audio input mute detection on all platforms

media/audio/alsa/alsa_input.h

 // Copyright 2013 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_ALSA_ALSA_INPUT_H_
 #define MEDIA_AUDIO_ALSA_ALSA_INPUT_H_
 
 #include <alsa/asoundlib.h>
 
 #include <string>
@@ skipping 31 matching lines @@
   virtual ~AlsaPcmInputStream();
 
   // Implementation of AudioInputStream.
   virtual bool Open() override;
   virtual void Start(AudioInputCallback* callback) override;
   virtual void Stop() override;
   virtual void Close() override;
   virtual double GetMaxVolume() override;
   virtual void SetVolume(double volume) override;
   virtual double GetVolume() override;
+  virtual bool IsMuted() override;
 
  private:
   // Logs the error and invokes any registered callbacks.
   void HandleError(const char* method, int error);
 
   // Reads one or more buffers of audio from the device, passes on to the
   // registered callback and schedules the next read.
   void ReadAudio();
 
   // Recovers from any device errors if possible.
@@ skipping 24 matching lines @@
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<AlsaPcmInputStream> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AlsaPcmInputStream);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_ALSA_ALSA_INPUT_H_