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

cc/resources/picture_layer_tiling.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_RESOURCES_PICTURE_LAYER_TILING_H_
 #define CC_RESOURCES_PICTURE_LAYER_TILING_H_
 
 #include <utility>
 #include <vector>
 
@@ skipping 138 matching lines @@
     return frame_time_in_seconds != last_impl_frame_time_in_seconds_;
   }
 
   scoped_ptr<base::Value> AsValue() const;
 
   static gfx::Rect ExpandRectEquallyToAreaBoundedBy(
       gfx::Rect starting_rect,
       int64 target_area,
       gfx::Rect bounding_rect);
 
+  bool has_ever_been_updated() const {
+    return last_impl_frame_time_in_seconds_ != 0.0;
+  }
+
  protected:
   typedef std::pair<int, int> TileMapKey;
   typedef base::hash_map<TileMapKey, scoped_refptr<Tile> > TileMap;
 
   PictureLayerTiling(float contents_scale,
                      gfx::Size layer_bounds,
                      PictureLayerTilingClient* client);
   void SetLiveTilesRect(gfx::Rect live_tiles_rect);
   void CreateTile(int i, int j);
   Tile* TileAt(int, int) const;
@@ skipping 14 matching lines @@
 
   friend class CoverageIterator;
 
  private:
   DISALLOW_ASSIGN(PictureLayerTiling);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_PICTURE_LAYER_TILING_H_