Add infrastructure for partial layouts

Source/core/rendering/RenderRegion.h

 /*
  * Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
  *    disclaimer.
@@ skipping 146 matching lines @@
 
 private:
     virtual const char* renderName() const { return "RenderRegion"; }
 
     virtual bool canHaveChildren() const OVERRIDE { return false; }
 
     virtual void insertedIntoTree() OVERRIDE;
     virtual void willBeRemovedFromTree() OVERRIDE;
 
     virtual void layoutBlock(bool relayoutChildren, LayoutUnit pageLogicalHeight = 0) OVERRIDE;
+    virtual bool supportsPartialLayout() const OVERRIDE { return false; }
     virtual void paintObject(PaintInfo&, const LayoutPoint&) OVERRIDE;
 
     virtual void installFlowThread();
 
     PassRefPtr<RenderStyle> computeStyleInRegion(const RenderObject*);
     void computeChildrenStyleInRegion(const RenderObject*);
     void setObjectStyleInRegion(RenderObject*, PassRefPtr<RenderStyle>, bool objectRegionStyleCached);
 
     void checkRegionStyle();
     void updateRegionHasAutoLogicalHeightFlag();
@@ skipping 49 matching lines @@
     ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderRegion());
     return static_cast<const RenderRegion*>(object);
 }
 
 // This will catch anyone doing an unnecessary cast.
 void toRenderRegion(const RenderRegion*);
 
 } // namespace WebCore
 
 #endif // RenderRegion_h