Don't run WSOLA over always muted channels.

media/cast/test/fake_media_source.cc

Index: media/cast/test/fake_media_source.cc
diff --git a/media/cast/test/fake_media_source.cc b/media/cast/test/fake_media_source.cc
index 06dd50a9719b0e72d76c7d928383c42bcb7c1ab6..fd3ae3b24e437d79680ef92e32b22796ac73fad3 100644
--- a/media/cast/test/fake_media_source.cc
+++ b/media/cast/test/fake_media_source.cc
@@ -251,7 +251,7 @@ void FakeMediaSource::Start(scoped_refptr<AudioFrameInput> audio_frame_input,
   }
 
   // Send transcoding streams.
-  audio_algo_.Initialize(source_audio_params_);
+  audio_algo_.Initialize(source_audio_params_, std::vector<bool>());
   audio_algo_.FlushBuffers();
   audio_fifo_input_bus_ = AudioBus::Create(
       source_audio_params_.channels(),