Move Node/ContainerNode's traverseToChildAt() to NodeTraversal

Source/core/dom/ContainerNode.h

Index: Source/core/dom/ContainerNode.h
diff --git a/Source/core/dom/ContainerNode.h b/Source/core/dom/ContainerNode.h
index 4ff3c6be47fc563b07523e52da7a079ff206b3f2..3750460ac8bd5bbe6b4948cfad9e59d40e00a9b6 100644
--- a/Source/core/dom/ContainerNode.h
+++ b/Source/core/dom/ContainerNode.h
@@ -75,7 +75,6 @@ public:
     PassRefPtrWillBeRawPtr<HTMLCollection> children();
 
     unsigned countChildren() const;
-    Node* traverseToChildAt(unsigned index) const;
 
     PassRefPtrWillBeRawPtr<Element> querySelector(const AtomicString& selectors, ExceptionState&);
     PassRefPtrWillBeRawPtr<StaticNodeList> querySelectorAll(const AtomicString& selectors, ExceptionState&);
@@ -281,13 +280,6 @@ inline unsigned Node::countChildren() const
     return toContainerNode(this)->countChildren();
 }
 
-inline Node* Node::traverseToChildAt(unsigned index) const
-{
-    if (!isContainerNode())
-        return 0;
-    return toContainerNode(this)->traverseToChildAt(index);
-}
-
 inline Node* Node::firstChild() const
 {
     if (!isContainerNode())