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 16 matching lines @@
 #include "core/dom/NodeRenderStyle.h"
 #include "core/dom/NodeRenderingContext.h"
 #include "core/dom/VisitedLinkState.h"
 #include "core/page/Page.h"
 
 namespace WebCore {
 
 void StyleResolverState::clear()
 {
     m_element = 0;
+    m_childIndex = 0;
     m_styledElement = 0;
     m_parentStyle = 0;
     m_parentNode = 0;
     m_regionForStyling = 0;
     m_elementStyleResources.clear();
 }
 
-void StyleResolverState::initElement(Element* element)
+void StyleResolverState::initElement(Element* element, int childIndex)
 {
     if (m_element == element)
         return;
 
     m_element = element;
     m_styledElement = element && element->isStyledElement() ? element : 0;
     m_elementLinkState = element ? element->document()->visitedLinkState()->determineLinkState(element) : NotInsideLink;
 
     if (!element || element != element->document()->documentElement())
         return;
 
     element->document()->setDirectionSetOnDocumentElement(false);
     element->document()->setWritingModeSetOnDocumentElement(false);
 }
 
-void StyleResolverState::initForStyleResolve(Document* document, Element* e, RenderStyle* parentStyle, RenderRegion* regionForStyling)
+void StyleResolverState::initForStyleResolve(Document* document, Element* e, int childIndex, RenderStyle* parentStyle, RenderRegion* regionForStyling)
 {
-    initElement(e);
+    initElement(e, childIndex);
 
     m_regionForStyling = regionForStyling;
 
     if (e) {
         NodeRenderingContext context(e);
         m_parentNode = context.parentNodeForRenderingAndStyle();
         m_parentStyle = context.resetStyleInheritance() ? 0 :
             parentStyle ? parentStyle :
             m_parentNode ? m_parentNode->renderStyle() : 0;
         m_distributedToInsertionPoint = context.insertionPoint();
     } else {
         m_parentNode = 0;
         m_parentStyle = parentStyle;
         m_distributedToInsertionPoint = false;
     }
 
     Node* docElement = e ? e->document()->documentElement() : 0;
     RenderStyle* docStyle = document->renderStyle();
     m_rootElementStyle = docElement && e != docElement ? docElement->renderStyle() : docStyle;
 
     m_style = 0;
     m_elementStyleResources.clear();
     m_fontDirty = false;
 
     if (Page* page = document->page())
         m_elementStyleResources.setDeviceScaleFactor(page->deviceScaleFactor());
 }
 
 } // namespace WebCore