[Chromecast] Implement new volume control API

chromecast/media/cma/backend/alsa/stream_mixer_alsa_input.h

Index: chromecast/media/cma/backend/alsa/stream_mixer_alsa_input.h
diff --git a/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input.h b/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input.h
index 7304108873d6519c133c735ab76dca3fd654c4e1..2d77008c56afc8c62a1412bcb0a8e0b6382bcaa7 100644
--- a/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input.h
+++ b/chromecast/media/cma/backend/alsa/stream_mixer_alsa_input.h
@@ -12,6 +12,7 @@
 #include "base/threading/thread_checker.h"
 #include "chromecast/media/cma/backend/alsa/media_pipeline_backend_alsa.h"
 #include "chromecast/public/media/media_pipeline_device_params.h"
+#include "chromecast/public/volume_control.h"
 
 namespace chromecast {
 namespace media {
@@ -52,7 +53,8 @@ class StreamMixerAlsaInput {
   StreamMixerAlsaInput(Delegate* delegate,
                        int samples_per_second,
                        bool primary,
-                       const std::string& device_id);
+                       const std::string& device_id,
+                       AudioContentType content_type);
   // Removes this input from the mixer, destroying the mixer if there are no
   // remaining inputs.
   ~StreamMixerAlsaInput();