[Chromecast] Implement new volume control API

chromecast/media/cma/backend/alsa/stream_mixer_alsa_unittest.cc

Index: chromecast/media/cma/backend/alsa/stream_mixer_alsa_unittest.cc
diff --git a/chromecast/media/cma/backend/alsa/stream_mixer_alsa_unittest.cc b/chromecast/media/cma/backend/alsa/stream_mixer_alsa_unittest.cc
index db5e3421bb6a6df36c083dd7299f3cf37db9b3f4..6574d673d83471852df6ba613423868705acd395 100644
--- a/chromecast/media/cma/backend/alsa/stream_mixer_alsa_unittest.cc
+++ b/chromecast/media/cma/backend/alsa/stream_mixer_alsa_unittest.cc
@@ -157,6 +157,9 @@ class MockInputQueue : public StreamMixerAlsa::InputQueue {
                void(const MediaPipelineBackendAlsa::RenderingDelay&
                         mixer_rendering_delay));
   std::string device_id() const override { return device_id_; }
+  AudioContentType content_type() const override {
+    return AudioContentType::kMedia;
+  }
   void set_filter_group(FilterGroup* group) override { filter_group_ = group; }
   FilterGroup* filter_group() override { return filter_group_; }
   int MaxReadSize() override { return max_read_size_; }
@@ -171,6 +174,9 @@ class MockInputQueue : public StreamMixerAlsa::InputQueue {
   MOCK_METHOD1(SignalError, void(StreamMixerAlsaInput::MixerError error));
   MOCK_METHOD1(PrepareToDelete, void(const OnReadyToDeleteCb& delete_cb));
 
+  void SetContentTypeVolume(float volume) override {}
+  void SetMuted(bool muted) override {}
+
   // Setters and getters for test control.
   void SetPaused(bool paused) { paused_ = paused; }
   void SetMaxReadSize(int max_read_size) { max_read_size_ = max_read_size; }