Get rid of a lot of special code for RenderFlowThread invalidation.

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 55 matching lines @@
 
     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;
-    void paintInvalidationOfFlowThreadContentRectangle(const LayoutRect& paintInvalidationRect, const LayoutRect& flowThreadPortionRect,
-        const LayoutRect& flowThreadPortionOverflowRect, const LayoutPoint& regionLocation);
 
 private:
     virtual void layoutBlock(bool relayoutChildren) override final;
 
 protected:
     RenderFlowThread* m_flowThread;
 
 private:
     LayoutRect m_flowThreadPortionRect;
     bool m_isValid : 1;
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderRegion, isRenderRegion());
 
 } // namespace blink
 
 #endif // RenderRegion_h