Update DOM code to use the new Traversal<HTML*Element> API

Source/core/dom/Node.cpp

Index: Source/core/dom/Node.cpp
diff --git a/Source/core/dom/Node.cpp b/Source/core/dom/Node.cpp
index 9164f891963939eb80c5b5ddbcd7c15e89b8656a..70ef7b6501e855d91e9e7893204154ad5d751263 100644
--- a/Source/core/dom/Node.cpp
+++ b/Source/core/dom/Node.cpp
@@ -2440,8 +2440,8 @@ void Node::unregisterScopedHTMLStyleChild()
 size_t Node::numberOfScopedHTMLStyleChildren() const
 {
     size_t count = 0;
-    for (Element* child = ElementTraversal::firstWithin(*this); child; child = ElementTraversal::nextSibling(*child)) {
-        if (child->hasTagName(HTMLNames::styleTag) && toHTMLStyleElement(child)->isRegisteredAsScoped())
+    for (HTMLStyleElement* style = Traversal<HTMLStyleElement>::firstChild(*this); style; style = Traversal<HTMLStyleElement>::nextSibling(*style)) {
+        if (style->isRegisteredAsScoped())
             ++count;
     }