Changing between multicol and regular block shouldn't recreate all renderers.

Source/core/rendering/style/RenderStyle.cpp

 /*
  * Copyright (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 162 matching lines @@
 {
     if ((!oldStyle && newStyle) || (oldStyle && !newStyle))
         return Reattach;
 
     if (!oldStyle && !newStyle)
         return NoChange;
 
     if (oldStyle->display() != newStyle->display()
         || oldStyle->hasPseudoStyle(FIRST_LETTER) != newStyle->hasPseudoStyle(FIRST_LETTER)
         || oldStyle->columnSpan() != newStyle->columnSpan()
-        || oldStyle->specifiesColumns() != newStyle->specifiesColumns()
         || !oldStyle->contentDataEquivalent(newStyle)
         || oldStyle->hasTextCombine() != newStyle->hasTextCombine())
         return Reattach;
 
     if (*oldStyle == *newStyle)
         return diffPseudoStyles(oldStyle, newStyle);
 
     if (oldStyle->inheritedNotEqual(newStyle)
         || oldStyle->hasExplicitlyInheritedProperties()
         || newStyle->hasExplicitlyInheritedProperties())
@@ skipping 1460 matching lines @@
     // right
     radiiSum = radii.topRight().height() + radii.bottomRight().height();
     if (radiiSum > rect.height())
         factor = std::min(rect.height() / radiiSum, factor);
 
     ASSERT(factor <= 1);
     return factor;
 }
 
 } // namespace WebCore