cc: Add mailbox support to ResourceProvider write locks.

cc/trees/layer_tree_host_impl.h

 // Copyright 2011 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_TREES_LAYER_TREE_HOST_IMPL_H_
 #define CC_TREES_LAYER_TREE_HOST_IMPL_H_
 
 #include <stddef.h>
 
 #include <bitset>
@@ skipping 733 matching lines @@
 
   OutputSurface* output_surface_;
 
   std::unique_ptr<ResourceProvider> resource_provider_;
   bool content_is_suitable_for_gpu_rasterization_;
   bool has_gpu_rasterization_trigger_;
   bool use_gpu_rasterization_;
   bool use_msaa_;
   GpuRasterizationStatus gpu_rasterization_status_;
   bool tree_resources_for_gpu_rasterization_dirty_;
+  std::unique_ptr<RasterBufferProvider> raster_buffer_provider_;
   std::unique_ptr<TileTaskManager> tile_task_manager_;
   std::unique_ptr<ResourcePool> resource_pool_;
   std::unique_ptr<Renderer> renderer_;
   std::unique_ptr<ImageDecodeController> image_decode_controller_;
 
   GlobalStateThatImpactsTilePriority global_tile_state_;
 
   // Tree currently being drawn.
   std::unique_ptr<LayerTreeImpl> active_tree_;
 
@@ skipping 102 matching lines @@
       fixed_raster_scale_attempted_scale_change_history_;
   std::unique_ptr<PendingTreeDurationHistogramTimer>
       pending_tree_duration_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_