Makes tile-creation lazy

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 38 matching lines @@
                                       gfx::Size* content_bounds) OVERRIDE;
   virtual skia::RefPtr<SkPicture> GetPicture() OVERRIDE;
 
   // PictureLayerTilingClient overrides.
   virtual scoped_refptr<Tile> CreateTile(PictureLayerTiling* tiling,
                                          gfx::Rect content_rect) OVERRIDE;
   virtual void UpdatePile(Tile* tile) OVERRIDE;
   virtual gfx::Size CalculateTileSize(
       gfx::Size current_tile_size,
       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();
-  void SyncTiling(
-      const PictureLayerTiling* tiling,
-      const Region& pending_layer_invalidation);
+  void SyncTiling(const PictureLayerTiling* tiling);
 
   void CreateTilingSet();
   void TransferTilingSet(scoped_ptr<PictureLayerTilingSet> tilings);
 
   // Mask-related functions
   void SetIsMask(bool is_mask);
   virtual ResourceProvider::ResourceId ContentsResourceId() const OVERRIDE;
 
   virtual bool AreVisibleResourcesReady() const OVERRIDE;
 
@@ skipping 44 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_