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

Source/core/css/resolver/StyleResolverState.cpp

Index: Source/core/css/resolver/StyleResolverState.cpp
diff --git a/Source/core/css/resolver/StyleResolverState.cpp b/Source/core/css/resolver/StyleResolverState.cpp
index 32d0fae7d390923816d43847d9fa6d0cea84c672..708c2a849a3487acddc1951face85dbe2d356a4a 100644
--- a/Source/core/css/resolver/StyleResolverState.cpp
+++ b/Source/core/css/resolver/StyleResolverState.cpp
@@ -34,6 +34,7 @@ namespace WebCore {
 void StyleResolverState::clear()
 {
     m_element = 0;
+    m_childIndex = 0;
     m_styledElement = 0;
     m_parentStyle = 0;
     m_parentNode = 0;
@@ -41,7 +42,7 @@ void StyleResolverState::clear()
     m_elementStyleResources.clear();
 }
 
-void StyleResolverState::initElement(Element* element)
+void StyleResolverState::initElement(Element* element, int childIndex)
 {
     if (m_element == element)
         return;
@@ -57,9 +58,9 @@ void StyleResolverState::initElement(Element* element)
     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;