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

remoting/host/win/audio_volume_filter_win.cc

Index: remoting/host/win/audio_volume_filter_win.cc
diff --git a/remoting/host/win/audio_volume_filter_win.cc b/remoting/host/win/audio_volume_filter_win.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2e6a12253c8aac64f79918cc931193474a92143e
--- /dev/null
+++ b/remoting/host/win/audio_volume_filter_win.cc
@@ -0,0 +1,58 @@
+// Copyright 2017 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/win/audio_volume_filter_win.h"
+
+#include "base/logging.h"
+
+namespace remoting {
+
+AudioVolumeFilterWin::AudioVolumeFilterWin(int silence_threshold)
+    : AudioVolumeFilter(silence_threshold) {}
+AudioVolumeFilterWin::~AudioVolumeFilterWin() = default;
+
+bool AudioVolumeFilterWin::ActivateBy(IMMDevice* mm_device) {
+  DCHECK(mm_device);
+  audio_volume_.Reset();
+  // TODO(zijiehe): Do we need to control the volume per process?
+  HRESULT hr = mm_device->Activate(__uuidof(IAudioEndpointVolume), CLSCTX_ALL,
+      nullptr, &audio_volume_);
+  if (FAILED(hr)) {
+    LOG(WARNING) << "Failed to get an IAudioEndpointVolume. Error " << hr;
+    return false;
+  }
+  return true;
+}
+
+float AudioVolumeFilterWin::GetAudioLevel() {
+  if (!audio_volume_) {
+    return 1;
+  }
+
+  BOOL mute;
+  HRESULT hr = audio_volume_->GetMute(&mute);
+  if (FAILED(hr)) {
+    LOG(ERROR) << "Failed to get mute status from IAudioEndpointVolume, error "
+               << hr;
+    return 1;
+  }
+  if (mute) {
+    return 0;
+  }
+
+  float level;
+  hr = audio_volume_->GetMasterVolumeLevelScalar(&level);
+  if (FAILED(hr) || level > 1) {
+    LOG(ERROR) << "Failed to get master volume from IAudioEndpointVolume, "
+                  "error "
+               << hr;
+    return 1;
+  }
+  if (level < 0) {
+    return 0;
+  }
+  return level;
+}
+
+}  // namespace remoting