cc: Fix impl-side painting flashing due to missing tiles

cc/layers/picture_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_PICTURE_LAYER_IMPL_H_
 #define CC_LAYERS_PICTURE_LAYER_IMPL_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 32 matching lines @@
   virtual void DidBecomeActive() OVERRIDE;
   virtual void DidLoseOutputSurface() OVERRIDE;
   virtual void CalculateContentsScale(float ideal_contents_scale,
                                       bool animating_transform_to_screen,
                                       float* contents_scale_x,
                                       float* contents_scale_y,
                                       gfx::Size* content_bounds) OVERRIDE;
   virtual skia::RefPtr<SkPicture> GetPicture() OVERRIDE;
 
   // PictureLayerTilingClient overrides.
-  virtual scoped_refptr<Tile> CreateTile(PictureLayerTiling* tiling,
+  virtual scoped_refptr<Tile> CreateTile(const PictureLayerTiling* tiling,
                                          gfx::Rect content_rect) OVERRIDE;
   virtual void UpdatePile(Tile* tile) OVERRIDE;
   virtual gfx::Size CalculateTileSize(
       gfx::Size content_bounds) OVERRIDE;
   virtual const Region* GetInvalidation() OVERRIDE;
   virtual const PictureLayerTiling* GetTwinTiling(
       const PictureLayerTiling* tiling) OVERRIDE;
 
   // PushPropertiesTo active tree => pending tree
   void SyncFromActiveLayer();
@@ skipping 56 matching lines @@
   bool raster_source_scale_was_animating_;
   bool is_using_lcd_text_;
 
   friend class PictureLayer;
   DISALLOW_COPY_AND_ASSIGN(PictureLayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_PICTURE_LAYER_IMPL_H_