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 fdeae92e6993e0db353683d9078c0d55f97c1b85..2f9c0904dfe996f0f305d32be1a3edc4d4988e37 100644
--- a/Source/core/css/resolver/StyleResolverState.cpp
+++ b/Source/core/css/resolver/StyleResolverState.cpp
@@ -45,6 +45,7 @@ void StyleResolverState::cacheBorderAndBackground()
 void StyleResolverState::clear()
 {
     m_element = 0;
+    m_childIndex = 0;
     m_styledElement = 0;
     m_parentStyle = 0;
     m_parentNode = 0;
@@ -54,9 +55,10 @@ void StyleResolverState::clear()
     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;
 }