Remove CSS regions support, keeping a bare minimum to support "region-based" multicol.

Source/core/rendering/RenderRegionSet.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
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 #ifndef RenderRegionSet_h
 #define RenderRegionSet_h
 
-#include "core/rendering/RenderBoxRegionInfo.h"
 #include "core/rendering/RenderRegion.h"
 
 namespace WebCore {
 
 class RenderFlowThread;
 
 // RenderRegionSet represents a set of regions that all have the same width and height. It is a "composite region box" that
 // can be used to represent a single run of contiguous regions.
 //
 // By combining runs of same-size columns or pages into a single object, we significantly reduce the number of unique RenderObjects
 // required to represent those objects.
 //
 // This class is abstract and is only intended for use by renderers that generate anonymous runs of identical regions, i.e.,
 // columns and printing. RenderMultiColumnSet and RenderPageSet represent runs of columns and pages respectively.
 //
 // FIXME: For now we derive from RenderRegion, but this may change at some point.
 
 class RenderRegionSet : public RenderRegion {
 public:
     RenderRegionSet(Element*, RenderFlowThread*);
 
-protected:
-    virtual bool shouldHaveAutoLogicalHeight() const OVERRIDE { return false; }
-
 private:
-    virtual void installFlowThread() OVERRIDE FINAL;
-
     virtual void expandToEncompassFlowThreadContentsIfNeeded() OVERRIDE FINAL;
 
     virtual const char* renderName() const = 0;
-
-    virtual bool isRenderRegionSet() const OVERRIDE FINAL { return true; }
 };
 
 } // namespace WebCore
 
 #endif // RenderRegionSet_h