Use new Traversal<HTML*Element> API in HTML code

Source/core/html/HTMLFieldSetElement.cpp

Index: Source/core/html/HTMLFieldSetElement.cpp
diff --git a/Source/core/html/HTMLFieldSetElement.cpp b/Source/core/html/HTMLFieldSetElement.cpp
index 65640c69e28a69409bd320ea002d7adf642a8e72..61d70db9287f01cadd466fb3ff80b201b75d2760 100644
--- a/Source/core/html/HTMLFieldSetElement.cpp
+++ b/Source/core/html/HTMLFieldSetElement.cpp
@@ -67,10 +67,8 @@ void HTMLFieldSetElement::disabledAttributeChanged()
 void HTMLFieldSetElement::childrenChanged(bool changedByParser, Node* beforeChange, Node* afterChange, int childCountDelta)
 {
     HTMLFormControlElement::childrenChanged(changedByParser, beforeChange, afterChange, childCountDelta);
-    for (Element* element = ElementTraversal::firstWithin(*this); element; element = ElementTraversal::nextSkippingChildren(*element, this)) {
-        if (element->hasTagName(legendTag))
-            invalidateDisabledStateUnder(*element);
-    }
+    for (HTMLLegendElement* legend = Traversal<HTMLLegendElement>::firstChild(*this); legend; legend = Traversal<HTMLLegendElement>::nextSibling(*legend))
+        invalidateDisabledStateUnder(*legend);
 }
 
 bool HTMLFieldSetElement::supportsFocus() const
@@ -91,11 +89,7 @@ RenderObject* HTMLFieldSetElement::createRenderer(RenderStyle*)
 
 HTMLLegendElement* HTMLFieldSetElement::legend() const
 {
-    for (Element* child = ElementTraversal::firstWithin(*this); child; child = ElementTraversal::nextSkippingChildren(*child, this)) {
-        if (child->hasTagName(legendTag))
-            return toHTMLLegendElement(child);
-    }
-    return 0;
+    return Traversal<HTMLLegendElement>::firstChild(*this);
 }
 
 PassRefPtr<HTMLCollection> HTMLFieldSetElement::elements()