cc: GPU rasterize tiles synchronously in PrepareToDraw.

cc/trees/layer_tree_host_impl.h

Index: cc/trees/layer_tree_host_impl.h
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index 64bc06450f3d47ef45add6f6a0583e7444f082ce..97b6c40e1a67e624b43edebfe8001567326e6cfc 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -29,6 +29,7 @@
 #include "cc/output/output_surface_client.h"
 #include "cc/output/renderer.h"
 #include "cc/quads/render_pass.h"
+#include "cc/resources/rasterizer.h"
 #include "cc/resources/resource_provider.h"
 #include "cc/resources/tile_manager.h"
 #include "cc/scheduler/commit_earlyout_reason.h"
@@ -499,6 +500,7 @@ class CC_EXPORT LayerTreeHostImpl
   // Only valid for synchronous (non-scheduled) single-threaded case.
   void SynchronouslyInitializeAllTiles();
 
+  virtual scoped_ptr<Rasterizer> CreateRasterizer();
   virtual void CreateResourceAndTileTaskWorkerPool(
       scoped_ptr<TileTaskWorkerPool>* tile_task_worker_pool,
       scoped_ptr<ResourcePool>* resource_pool,
@@ -611,6 +613,7 @@ class CC_EXPORT LayerTreeHostImpl
   bool use_gpu_rasterization_;
   GpuRasterizationStatus gpu_rasterization_status_;
   scoped_ptr<TileTaskWorkerPool> tile_task_worker_pool_;
+  scoped_ptr<Rasterizer> rasterizer_;
   scoped_ptr<ResourcePool> resource_pool_;
   scoped_ptr<ResourcePool> staging_resource_pool_;
   scoped_ptr<Renderer> renderer_;