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

remoting/host/audio_silence_detector.cc

Index: remoting/host/audio_silence_detector.cc
diff --git a/remoting/host/audio_silence_detector.cc b/remoting/host/audio_silence_detector.cc
index a744b35a117f5772be80ff8435f1a5c9ac7388ff..9f125458f4236a0074e06648a9675e039ebac9ed 100644
--- a/remoting/host/audio_silence_detector.cc
+++ b/remoting/host/audio_silence_detector.cc
@@ -20,7 +20,8 @@ int kSilencePeriodThresholdSeconds = 1;
 AudioSilenceDetector::AudioSilenceDetector(int threshold)
     : threshold_(threshold),
       silence_length_max_(0),
-      silence_length_(0) {
+      silence_length_(0),
+      channels_(0) {
   DCHECK_GE(threshold_, 0);
 }
 
@@ -29,18 +30,21 @@ AudioSilenceDetector::~AudioSilenceDetector() {
 
 void AudioSilenceDetector::Reset(int sampling_rate, int channels) {
   DCHECK_GT(sampling_rate, 0);
+  DCHECK_GT(channels, 0);
   silence_length_ = 0;
   silence_length_max_ =
       sampling_rate * channels * kSilencePeriodThresholdSeconds;
+  channels_ = channels;
 }
 
 bool AudioSilenceDetector::IsSilence(const int16_t* samples,
-                                     size_t samples_count) {
+                                     size_t frames) {
+  const int samples_count = frames * channels();
   bool silent_packet = true;
   // Potentially this loop can be optimized (e.g. using SSE or adding special
   // case for threshold_==0), but it's not worth worrying about because the
   // amount of data it processes is relaively small.
-  for (size_t i = 0; i < samples_count; ++i) {
+  for (int i = 0; i < samples_count; ++i) {
     if (abs(samples[i]) > threshold_) {
       silent_packet = false;
       break;
@@ -56,4 +60,8 @@ bool AudioSilenceDetector::IsSilence(const int16_t* samples,
   return silence_length_ > silence_length_max_;
 }
 
+int AudioSilenceDetector::channels() const {
+  return channels_;
+}
+
 }  // namespace remoting