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

remoting/host/audio_capturer_linux.cc

 // 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.
 
 #include "remoting/host/audio_capturer_linux.h"
 
 #include <stdint.h>
 
 #include <utility>
 
@@ skipping 41 matching lines @@
   pipe_reader_->AddObserver(this);
   return true;
 }
 
 void AudioCapturerLinux::OnDataRead(
     scoped_refptr<base::RefCountedString> data) {
   DCHECK(!callback_.is_null());
 
   if (silence_detector_.IsSilence(
           reinterpret_cast<const int16_t*>(data->data().data()),
-          data->data().size() / sizeof(int16_t))) {
+          data->data().size() / sizeof(int16_t) / AudioPipeReader::kChannels)) {
     return;
   }
 
   std::unique_ptr<AudioPacket> packet(new AudioPacket());
   packet->add_data(data->data());
   packet->set_encoding(AudioPacket::ENCODING_RAW);
   packet->set_sampling_rate(AudioPipeReader::kSamplingRate);
   packet->set_bytes_per_sample(AudioPipeReader::kBytesPerSample);
   packet->set_channels(AudioPipeReader::kChannels);
   callback_.Run(std::move(packet));
 }
 
 bool AudioCapturer::IsSupported() {
   return g_pulseaudio_pipe_sink_reader.Get().get() != nullptr;
 }
 
 std::unique_ptr<AudioCapturer> AudioCapturer::Create() {
   scoped_refptr<AudioPipeReader> reader =
       g_pulseaudio_pipe_sink_reader.Get();
   if (!reader.get())
     return nullptr;
   return base::WrapUnique(new AudioCapturerLinux(reader));
 }
 
 }  // namespace remoting