cc: Do bitmap conversion for RasterBuffer in the worker thread.

cc/test/fake_tile_manager.cc

Index: cc/test/fake_tile_manager.cc
diff --git a/cc/test/fake_tile_manager.cc b/cc/test/fake_tile_manager.cc
index d15819d737712612e8e29a874eb363f31800c9b1..2fb9750a01c1d14609d108101e372149f1cd45e2 100644
--- a/cc/test/fake_tile_manager.cc
+++ b/cc/test/fake_tile_manager.cc
@@ -48,7 +48,7 @@ class FakeRasterizerImpl : public Rasterizer, public RasterizerTaskClient {
   }
 
   // Overridden from RasterizerTaskClient:
-  virtual SkCanvas* AcquireCanvasForRaster(RasterTask* task) OVERRIDE {
+  virtual RasterCanvas* AcquireCanvasForRaster(RasterTask* task) OVERRIDE {
     return NULL;
   }
   virtual void ReleaseCanvasForRaster(RasterTask* task) OVERRIDE {}