Avoid N^2 walk placing renderers when building the render tree

Source/core/css/resolver/StyleResolverState.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 27 matching lines @@
     if (m_hasUAAppearance) {
         m_borderData = m_style->border();
         m_backgroundData = *m_style->backgroundLayers();
         m_backgroundColor = m_style->backgroundColor();
     }
 }
 
 void StyleResolverState::clear()
 {
     m_element = 0;
+    m_childIndex = 0;
     m_styledElement = 0;
     m_parentStyle = 0;
     m_parentNode = 0;
     m_regionForStyling = 0;
     m_pendingImageProperties.clear();
     m_hasPendingShaders = false;
     m_pendingSVGDocuments.clear();
 }
 
-void StyleResolverState::initElement(Element* e)
+void StyleResolverState::initElement(Element* e, int childIndex)
 {
     m_element = e;
+    m_childIndex = childIndex;
     m_styledElement = e && e->isStyledElement() ? static_cast<StyledElement*>(e) : 0;
     m_elementLinkState = e ? e->document()->visitedLinkState()->determineLinkState(e) : NotInsideLink;
 }
 
 void StyleResolverState::initForStyleResolve(Document* document, Element* e, RenderStyle* parentStyle, RenderRegion* regionForStyling)
 {
     m_regionForStyling = regionForStyling;
 
     if (e) {
         NodeRenderingContext context(e);
@@ skipping 74 matching lines @@
         return RenderTheme::focusRingColor();
     case CSSValueCurrentcolor:
         return style()->color();
     default:
         return colorForCSSValue(ident);
     }
 }
 
 
 } // namespace WebCore