[Chromecast] Add new volume control API to CastMediaShlib

chromecast/media/cma/backend/media_pipeline_backend_factory.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chromecast/media/cma/backend/media_pipeline_backend_factory.h"
 
 #include "chromecast/media/cma/backend/media_pipeline_backend_manager.h"
 #include "chromecast/public/media/media_pipeline_backend.h"
 #include "chromecast/public/media/media_pipeline_device_params.h"
 
 namespace chromecast {
 namespace media {
 
 MediaPipelineBackendFactory::MediaPipelineBackendFactory(
     MediaPipelineBackendManager* media_pipeline_backend_manager)
     : media_pipeline_backend_manager_(media_pipeline_backend_manager) {
   DCHECK(media_pipeline_backend_manager_);
 }
 
 MediaPipelineBackendFactory::~MediaPipelineBackendFactory() {}
 
 std::unique_ptr<MediaPipelineBackend>
 MediaPipelineBackendFactory::CreateBackend(
-    const MediaPipelineDeviceParams& params,
-    const std::string& audio_device_id) {
+    const MediaPipelineDeviceParams& params) {
   return media_pipeline_backend_manager_->CreateMediaPipelineBackend(params);
 }
 
 }  // namespace media
 }  // namespace chromecast