Style changes to visual overflow do not require a layout

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 440 matching lines @@
             return true;
 
         if (rareNonInheritedData->m_deprecatedFlexibleBox.get() != other.rareNonInheritedData->m_deprecatedFlexibleBox.get()
             && *rareNonInheritedData->m_deprecatedFlexibleBox.get() != *other.rareNonInheritedData->m_deprecatedFlexibleBox.get())
             return true;
 
         if (rareNonInheritedData->m_flexibleBox.get() != other.rareNonInheritedData->m_flexibleBox.get()
             && *rareNonInheritedData->m_flexibleBox.get() != *other.rareNonInheritedData->m_flexibleBox.get())
             return true;
 
-        // FIXME: We should add an optimized form of layout that just recomputes visual overflow.
-        if (!rareNonInheritedData->shadowDataEquivalent(*other.rareNonInheritedData.get()))
-            return true;
-
         if (!rareNonInheritedData->reflectionDataEquivalent(*other.rareNonInheritedData.get()))
             return true;
 
         if (rareNonInheritedData->m_multiCol.get() != other.rareNonInheritedData->m_multiCol.get()
             && *rareNonInheritedData->m_multiCol.get() != *other.rareNonInheritedData->m_multiCol.get())
             return true;
 
         // If the counter directives change, trigger a relayout to re-calculate counter values and rebuild the counter node tree.
         const CounterDirectiveMap* mapA = rareNonInheritedData->m_counterDirectives.get();
         const CounterDirectiveMap* mapB = other.rareNonInheritedData->m_counterDirectives.get();
@@ skipping 182 matching lines @@
             || rareInheritedData->userSelect != other.rareInheritedData->userSelect
             || rareInheritedData->m_imageRendering != other.rareInheritedData->m_imageRendering)
             return true;
     }
 
     if (rareNonInheritedData.get() != other.rareNonInheritedData.get()) {
         if (rareNonInheritedData->userDrag != other.rareNonInheritedData->userDrag
             || rareNonInheritedData->m_borderFit != other.rareNonInheritedData->m_borderFit
             || rareNonInheritedData->m_objectFit != other.rareNonInheritedData->m_objectFit
             || rareNonInheritedData->m_objectPosition != other.rareNonInheritedData->m_objectPosition
+            || !rareNonInheritedData->shadowDataEquivalent(*other.rareNonInheritedData.get())
             || !dataEquivalent(rareNonInheritedData->m_shapeOutside, other.rareNonInheritedData->m_shapeOutside)
             || !dataEquivalent(rareNonInheritedData->m_clipPath, other.rareNonInheritedData->m_clipPath))
             return true;
     }
 
     return false;
 }
 
 void RenderStyle::updatePropertySpecificDifferences(const RenderStyle& other, StyleDifference& diff) const
 {
@@ skipping 1067 matching lines @@
         horizontal || includeLogicalRightEdge);
 
     edges[BSLeft] = BorderEdge(borderLeftWidth(),
         visitedDependentColor(CSSPropertyBorderLeftColor),
         borderLeftStyle(),
         borderLeftIsTransparent(),
         !horizontal || includeLogicalLeftEdge);
 }
 
 } // namespace blink