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

remoting/host/audio_capturer_linux.cc

Index: remoting/host/audio_capturer_linux.cc
diff --git a/remoting/host/audio_capturer_linux.cc b/remoting/host/audio_capturer_linux.cc
index 9c4272053817e98442db5ed117645c3d1851496f..a5a54d443209e4fc95555fe26bd7fe8c47e48097 100644
--- a/remoting/host/audio_capturer_linux.cc
+++ b/remoting/host/audio_capturer_linux.cc
@@ -59,7 +59,7 @@ void AudioCapturerLinux::OnDataRead(
 
   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;
   }