Add a silent audio sink to consume WebAudio data on silence detection.

media/base/audio_bus.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_BASE_AUDIO_BUS_H_
 #define MEDIA_BASE_AUDIO_BUS_H_
 
 #include <vector>
 
 #include "base/memory/aligned_memory.h"
@@ skipping 83 matching lines @@
 
   int channels() const { return static_cast<int>(channel_data_.size()); }
   int frames() const { return frames_; }
   void set_frames(int frames);
 
   // Helper method for zeroing out all channels of audio data.
   void Zero();
   void ZeroFrames(int frames);
   void ZeroFramesPartial(int start_frame, int frames);
 
+  // Checks if all frames are zero.
+  bool AreFramesZero() const;
+
   // Scale internal channel values by |volume| >= 0.  If an invalid value
   // is provided, no adjustment is done.
   void Scale(float volume);
 
   // Swaps channels identified by |a| and |b|.  The caller needs to make sure
   // the channels are valid.
   void SwapChannels(int a, int b);
 
   virtual ~AudioBus();
 
@@ skipping 34 matching lines @@
 
   AudioBusRefCounted(int channels, int frames);
   ~AudioBusRefCounted() override;
 
   DISALLOW_COPY_AND_ASSIGN(AudioBusRefCounted);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_AUDIO_BUS_H_