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

cc/resources/picture_layer_tiling.h

Index: cc/resources/picture_layer_tiling.h
diff --git a/cc/resources/picture_layer_tiling.h b/cc/resources/picture_layer_tiling.h
index 66ade477c7cf992a3b14f620c7daa585dcb49d92..cdb34d43ee5faed23ff87cf2a69b86c4fb3e668c 100644
--- a/cc/resources/picture_layer_tiling.h
+++ b/cc/resources/picture_layer_tiling.h
@@ -157,6 +157,10 @@ class CC_EXPORT PictureLayerTiling {
       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;