[Chromecast] Remove command-line switch to change the number of mixer output channels

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

Index: chromecast/media/cma/backend/alsa/stream_mixer_alsa.h
diff --git a/chromecast/media/cma/backend/alsa/stream_mixer_alsa.h b/chromecast/media/cma/backend/alsa/stream_mixer_alsa.h
index 875361116dcd4167e2e2476f1f40d01255cedabd..58a51ec1e1b11420b794401d31c9204f3097c290 100644
--- a/chromecast/media/cma/backend/alsa/stream_mixer_alsa.h
+++ b/chromecast/media/cma/backend/alsa/stream_mixer_alsa.h
@@ -120,7 +120,6 @@ class StreamMixerAlsa {
   int output_samples_per_second() const { return output_samples_per_second_; }
   bool empty() const { return inputs_.empty(); }
   State state() const { return state_; }
-  int num_output_channels() const { return num_output_channels_; }
 
   const scoped_refptr<base::SingleThreadTaskRunner>& task_runner() const {
     return mixer_task_runner_;
@@ -206,7 +205,6 @@ class StreamMixerAlsa {
   // User-configurable ALSA parameters. This caches the results, so the code
   // only has to interact with the command line parameters once.
   std::string alsa_device_name_;
-  int num_output_channels_;
   snd_pcm_uframes_t alsa_buffer_size_;
   bool alsa_period_explicitly_set;
   snd_pcm_uframes_t alsa_period_size_;