cc: Use const ref to avoid extra ref count of VideoProviderClientImpl.

cc/layers/video_layer_impl.h

 // Copyright 2012 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.
 
 #ifndef CC_LAYERS_VIDEO_LAYER_IMPL_H_
 #define CC_LAYERS_VIDEO_LAYER_IMPL_H_
 
 #include <vector>
 
 #include "cc/base/cc_export.h"
@@ skipping 30 matching lines @@
   void DidBecomeActive() override;
   void ReleaseResources() override;
 
   void SetNeedsRedraw();
   media::VideoRotation video_rotation() const { return video_rotation_; }
 
  private:
   VideoLayerImpl(
       LayerTreeImpl* tree_impl,
       int id,
-      scoped_refptr<VideoFrameProviderClientImpl> provider_client_impl,
+      const scoped_refptr<VideoFrameProviderClientImpl>& provider_client_impl,
       media::VideoRotation video_rotation);
 
   const char* LayerTypeAsString() const override;
 
   scoped_refptr<VideoFrameProviderClientImpl> provider_client_impl_;
 
   scoped_refptr<media::VideoFrame> frame_;
 
   media::VideoRotation video_rotation_;
 
   scoped_ptr<VideoResourceUpdater> updater_;
   VideoFrameExternalResources::ResourceType frame_resource_type_;
   std::vector<ResourceProvider::ResourceId> frame_resources_;
 
   // TODO(danakj): Remove these, hide software path inside ResourceProvider and
   // ExternalResource (aka TextureMailbox) classes.
   std::vector<unsigned> software_resources_;
   // Called once for each software resource.
   ReleaseCallbackImpl software_release_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoLayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_VIDEO_LAYER_IMPL_H_