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

remoting/host/audio_volume_filter_unittest.cc

Index: remoting/host/audio_volume_filter_unittest.cc
diff --git a/remoting/host/audio_volume_filter_unittest.cc b/remoting/host/audio_volume_filter_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..94cc0a75e4a6ade7ed48be59f2737d14156dfd08
--- /dev/null
+++ b/remoting/host/audio_volume_filter_unittest.cc
@@ -0,0 +1,79 @@
+// 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/audio_volume_filter.h"
+
+#include "base/macros.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace remoting {
+
+namespace {
+
+class FakeAudioVolumeFilter : public AudioVolumeFilter {
+ public:
+  FakeAudioVolumeFilter(int silence_threshold)
+      : AudioVolumeFilter(silence_threshold) {}
+  ~FakeAudioVolumeFilter() override = default;
+
+  void set_audio_level(float level) { level_ = level; }
+
+ protected:
+  float GetAudioLevel() override { return level_; }
+
+ private:
+  float level_ = 0;
+};
+
+}  // namespace
+
+TEST(AudioVolumeFilterTest, TwoChannels) {
+  int16_t samples[] =
+      {1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10};
+  FakeAudioVolumeFilter filter(0);
+  filter.set_audio_level(0.5f);
+  filter.Initialize(9, 2);
+  // After applying the audio volume, the |samples| should still pass the
+  // AudioSilenceDetector, AudioVolumeFilter::Apply() returns true under this
+  // condition. Ditto.
+  ASSERT_TRUE(filter.Apply(samples, arraysize(samples) / 2));
+}
+
+TEST(AudioVolumeFilterTest, ThreeChannels) {
+  int16_t samples[] =
+      {1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11};
+  FakeAudioVolumeFilter filter(0);
+  filter.set_audio_level(0.5f);
+  filter.Initialize(6, 3);
+  ASSERT_TRUE(filter.Apply(samples, arraysize(samples) / 3));
+}
+
+TEST(AudioVolumeFilterTest, SilentSamples) {
+  int16_t samples[] =
+      {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+  FakeAudioVolumeFilter filter(0);
+  filter.set_audio_level(0.5f);
+  filter.Initialize(9, 2);
+  ASSERT_FALSE(filter.Apply(samples, arraysize(samples) / 2));
+}
+
+TEST(AudioVolumeFilterTest, AudioLevel0) {
+  int16_t samples[] =
+      {1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10};
+  FakeAudioVolumeFilter filter(0);
+  filter.set_audio_level(0);
+  filter.Initialize(9, 2);
+  ASSERT_FALSE(filter.Apply(samples, arraysize(samples) / 2));
+}
+
+TEST(AudioVolumeFilterTest, SilentAfterApplying) {
+  int16_t samples[] =
+      {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
+  FakeAudioVolumeFilter filter(0);
+  filter.set_audio_level(0.9f);
+  filter.Initialize(9, 2);
+  ASSERT_TRUE(filter.Apply(samples, arraysize(samples) / 2));
+}
+
+}  // namespace remoting