Make HTMLCollection / NodeList backward traversal consistent with forward one

Source/core/dom/Element.cpp

Index: Source/core/dom/Element.cpp
diff --git a/Source/core/dom/Element.cpp b/Source/core/dom/Element.cpp
index 846516ce3605984a87350bcafce8b33ab1f13480..353c97418c4ac71d3feae799436b4c975fedab7e 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -1853,7 +1853,7 @@ void Element::checkForSiblingStyleChanges(bool finishedParsingCallback, Node* be
     // In the DOM case, we only need to do something if |afterChange| is not 0.
     if (childrenAffectedByLastChildRules() && beforeChange) {
         // Find our new last child.
-        Node* newLastChild = ElementTraversal::lastWithin(*this);
+        Node* newLastChild = ElementTraversal::lastChild(*this);
         RenderStyle* newLastChildStyle = newLastChild ? newLastChild->renderStyle() : 0;
 
         // Find the last element node going backwards from |beforeChange|