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

Source/core/dom/Element.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2013 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
@@ skipping 392 matching lines @@
     void cloneDataFromElement(const Element&);
 
     bool hasEquivalentAttributes(const Element* other) const;
 
     virtual void copyNonAttributePropertiesFromElement(const Element&) { }
 
     virtual void attach();
     virtual void detach();
     virtual RenderObject* createRenderer(RenderArena*, RenderStyle*);
     virtual bool rendererIsNeeded(const NodeRenderingContext&);
-    void recalcStyle(StyleChange = NoChange);
+    void recalcStyle(StyleChange = NoChange, int childIndex = 0);
     void didAffectSelector(AffectedSelectorMask);
 
     ElementShadow* shadow() const;
     ElementShadow* ensureShadow();
     PassRefPtr<ShadowRoot> createShadowRoot(ExceptionCode&);
     ShadowRoot* shadowRoot() const;
 
     bool hasAuthorShadowRoot() const { return shadowRoot(); }
 
     ShadowRoot* userAgentShadowRoot() const;
@@ skipping 142 matching lines @@
     // W3C API
     void webkitRequestFullscreen();
 
     bool isInTopLayer() const;
     void setIsInTopLayer(bool);
 
     void webkitRequestPointerLock();
 
     bool isSpellCheckingEnabled() const;
 
-    PassRefPtr<RenderStyle> styleForRenderer();
-    PassRefPtr<RenderStyle> originalStyleForRenderer();
+    PassRefPtr<RenderStyle> styleForRenderer(int childIndex = 0);
+    PassRefPtr<RenderStyle> originalStyleForRenderer(int childIndex = 0);
 
     RenderRegion* renderRegion() const;
     const AtomicString& webkitRegionOverset() const;
     Vector<RefPtr<Range> > webkitGetRegionFlowRanges() const;
 
     bool hasID() const;
     bool hasClass() const;
     const SpaceSplitString& classNames() const;
 
     IntSize savedLayerScrollOffset() const;
@@ skipping 406 matching lines @@
 
 inline const Attribute* ElementData::attributeItem(unsigned index) const
 {
     RELEASE_ASSERT(index < length());
     return attributeBase() + index;
 }
 
 } // namespace
 
 #endif