[Chromecast] Cleanup the API for creating MediaPipelineBackend.

chromecast/media/audio/cast_audio_output_stream_unittest.cc

Index: chromecast/media/audio/cast_audio_output_stream_unittest.cc
diff --git a/chromecast/media/audio/cast_audio_output_stream_unittest.cc b/chromecast/media/audio/cast_audio_output_stream_unittest.cc
index a6679d8588afa61ba9e882bd0285a7169aeb1e35..f96ebc3510a2713f9f5d540fd1a0a11234dce18b 100644
--- a/chromecast/media/audio/cast_audio_output_stream_unittest.cc
+++ b/chromecast/media/audio/cast_audio_output_stream_unittest.cc
@@ -182,7 +182,8 @@ class FakeAudioManager : public CastAudioManager {
   ~FakeAudioManager() override {}
 
   // CastAudioManager overrides.
-  scoped_ptr<MediaPipelineBackend> CreateMediaPipelineBackend() override {
+  scoped_ptr<MediaPipelineBackend> CreateMediaPipelineBackend(
+      const MediaPipelineDeviceParams& params) override {
     DCHECK(media::MediaMessageLoop::GetTaskRunner()->BelongsToCurrentThread());
     DCHECK(!media_pipeline_backend_);