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

Source/core/rendering/RenderMultiColumnSet.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 79 matching lines @@
     virtual void paintObject(PaintInfo&, const LayoutPoint& paintOffset) OVERRIDE;
 
     virtual LayoutUnit pageLogicalWidth() const OVERRIDE { return m_computedColumnWidth; }
     virtual LayoutUnit pageLogicalHeight() const OVERRIDE { return m_computedColumnHeight; }
 
     virtual LayoutUnit pageLogicalTopForOffset(LayoutUnit offset) const OVERRIDE;
 
     // FIXME: This will change once we have column sets constrained by enclosing pages, etc.
     virtual LayoutUnit logicalHeightOfAllFlowThreadContent() const OVERRIDE { return m_computedColumnHeight; }
 
-    // FIXME: For now we return false, but it's likely we will leverage the auto height region code to do column
-    // balancing. That's why we have an override of this function that is distinct from RenderRegionSet's override.
-    virtual bool shouldHaveAutoLogicalHeight() const OVERRIDE { return false; }
-
     virtual void repaintFlowThreadContent(const LayoutRect& repaintRect) const OVERRIDE;
 
     virtual void collectLayerFragments(LayerFragments&, const LayoutRect& layerBoundingBox, const LayoutRect& dirtyRect) OVERRIDE;
 
     virtual const char* renderName() const OVERRIDE;
 
     void paintColumnRules(PaintInfo&, const LayoutPoint& paintOffset);
 
     LayoutUnit columnGap() const;
     LayoutRect columnRectAt(unsigned index) const;
@@ skipping 57 matching lines @@
     };
     Vector<ContentRun, 1> m_contentRuns;
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderMultiColumnSet, isRenderMultiColumnSet());
 
 } // namespace WebCore
 
 #endif // RenderMultiColumnSet_h