Add infrastructure for partial layouts

Source/core/rendering/RenderLazyBlock.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 47 matching lines @@
 private:
     virtual void paintChildren(PaintInfo&, const LayoutPoint&) OVERRIDE;
 
     virtual bool isRenderLazyBlock() const OVERRIDE { return true; }
     virtual void willBeDestroyed() OVERRIDE;
     virtual void willBeRemovedFromTree() OVERRIDE;
     virtual void layoutBlock(bool relayoutChildren, LayoutUnit pageLogicalHeight) OVERRIDE;
 
     void layoutChildren(bool relayoutChildren);
 
+    virtual bool supportsPartialLayout() const OVERRIDE { return false; }
+
     void attachLazyBlock();
     void detachLazyBlock();
 
     RenderLazyBlock* m_next;
     RenderLazyBlock* m_previous;
     RenderBox* m_firstVisibleChildBox;
     RenderBox* m_lastVisibleChildBox;
     bool m_attached;
     bool m_isNestedLayout;
     LayoutRect m_intersectRect;
     IntRect m_expandedViewportRect;
 };
 
 inline RenderLazyBlock* toRenderLazyBlock(RenderObject* object)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderLazyBlock());
     return static_cast<RenderLazyBlock*>(object);
 }
 
 inline const RenderLazyBlock* toRenderLazyBlock(const RenderObject* object)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderLazyBlock());
     return static_cast<const RenderLazyBlock*>(object);
 }
 
 } // namespace WebCore
 
 #endif // RenderLazyBlock_h