[New Multicolumn] Preparatory work for nested multicol support.

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 24 matching lines @@
 namespace blink {
 
 class RenderFlowThread;
 
 class RenderRegion : public RenderBlockFlow {
 public:
     explicit RenderRegion(Element*, RenderFlowThread*);
 
     virtual bool isOfType(LayoutObjectType type) const override { return type == LayoutObjectRenderRegion || RenderBlockFlow::isOfType(type); }
 
-    void setFlowThreadPortionRect(const LayoutRect& rect) { m_flowThreadPortionRect = rect; }
-    LayoutRect flowThreadPortionRect() const { return m_flowThreadPortionRect; }
+    virtual LayoutRect flowThreadPortionRect() const = 0;
     LayoutRect flowThreadPortionOverflowRect() const;
+    LayoutRect overflowRectForFlowThreadPortion(const LayoutRect& flowThreadPortionRect, bool isFirstPortion, bool isLastPortion) const;
 
     RenderFlowThread* flowThread() const { return m_flowThread; }
 
     // Valid regions do not create circular dependencies with other flows.
     bool isValid() const { return m_isValid; }
     void setIsValid(bool valid) { m_isValid = valid; }
 
     bool isFirstRegion() const;
     bool isLastRegion() const;
 
     // These methods represent the width and height of a "page" and for a RenderRegion they are just
     // the content width and content height of a region. For RenderMultiColumnSets, however, they
     // will be the width and height of a single column or page in the set.
     virtual LayoutUnit pageLogicalWidth() const;
     virtual LayoutUnit pageLogicalHeight() const;
 
     virtual bool canHaveChildren() const override final { return false; }
     virtual bool canHaveGeneratedChildren() const override final { return true; }
 
     virtual const char* renderName() const override { return "RenderRegion"; }
 
 protected:
     virtual void computeIntrinsicLogicalWidths(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const override final;
 
-    LayoutRect overflowRectForFlowThreadPortion(const LayoutRect& flowThreadPortionRect, bool isFirstPortion, bool isLastPortion) const;
-
 private:
     virtual void layoutBlock(bool relayoutChildren) override final;
 
 protected:
     RenderFlowThread* m_flowThread;
 
 private:
-    LayoutRect m_flowThreadPortionRect;
     bool m_isValid : 1;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(RenderRegion, isRenderRegion());
 
 } // namespace blink
 
 #endif // RenderRegion_h