Add infrastructure for partial layouts

Source/core/rendering/RenderMultiColumnBlock.h

 /*
  * Copyright (C) 2012 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 41 matching lines @@
     virtual const char* renderName() const;
 
     virtual RenderObject* layoutSpecialExcludedChild(bool relayoutChildren) OVERRIDE;
 
     virtual void styleDidChange(StyleDifference, const RenderStyle*) OVERRIDE;
 
     virtual bool updateLogicalWidthAndColumnWidth() OVERRIDE;
     virtual void checkForPaginationLogicalHeightChange(LayoutUnit& pageLogicalHeight, bool& pageLogicalHeightChanged, bool& hasSpecifiedPageLogicalHeight) OVERRIDE;
     virtual bool relayoutForPagination(bool hasSpecifiedPageLogicalHeight, LayoutUnit pageLogicalHeight, LayoutStateMaintainer&) OVERRIDE;
 
+    virtual bool supportsPartialLayout() const OVERRIDE { return false; }
+
     virtual void addChild(RenderObject* newChild, RenderObject* beforeChild = 0) OVERRIDE;
 
     void computeColumnCountAndWidth();
 
     void ensureColumnSets();
 
     RenderMultiColumnFlowThread* m_flowThread;
     unsigned m_columnCount;   // The default column count/width that are based off our containing block width. These values represent only the default,
     LayoutUnit m_columnWidth; // since a multi-column block that is split across variable width pages or regions will have different column counts and widths in each.
                               // These values will be cached (eventually) for multi-column blocks.
@@ skipping 13 matching lines @@
     return static_cast<const RenderMultiColumnBlock*>(object);
 }
 
 // This will catch anyone doing an unnecessary cast.
 void toRenderMultiColumnBlock(const RenderMultiColumnBlock*);
 
 } // namespace WebCore
 
 #endif // RenderMultiColumnBlock_h