[Chromoting] Add AudioVolumeApplier to reduce the complexity and the dependency of kChannels

remoting/host/audio_silence_detector.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 REMOTING_HOST_AUDIO_SILENCE_DETECTOR_H_
 #define REMOTING_HOST_AUDIO_SILENCE_DETECTOR_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/logging.h"
 
 namespace remoting {
 
 // Helper used in audio capturers to detect and drop silent audio packets.
 class AudioSilenceDetector {
  public:
   // |threshold| is used to specify maximum absolute sample value that should
   // still be considered as silence.
   explicit AudioSilenceDetector(int threshold);
   ~AudioSilenceDetector();
 
   void Reset(int sampling_rate, int channels);
 
   // Must be called for each new chunk of data. Return true the given packet
   // is silence should be dropped.
-  bool IsSilence(const int16_t* samples, size_t samples_count);
+  bool IsSilence(const int16_t* samples, size_t frames);
+
+  // The count of channels received from last Reset().
+  int channels() const;
 
  private:
   // Maximum absolute sample value that should still be considered as silence.
   int threshold_;
 
   // Silence period threshold in samples. Silence intervals shorter than this
   // value are still encoded and sent to the client, so that we don't disrupt
   // playback by dropping them.
   int silence_length_max_;
 
   // Lengths of the current silence period in samples.
   int silence_length_;
+
+  // The count of channels.
+  int channels_;
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_HOST_AUDIO_SILENCE_DETECTOR_H_