Use new Traversal<*Element> API in svg code for clarity

Source/core/svg/SVGElement.cpp

Index: Source/core/svg/SVGElement.cpp
diff --git a/Source/core/svg/SVGElement.cpp b/Source/core/svg/SVGElement.cpp
index b7cc6bdda1f7d01b8eed762170494543f58f74fe..c3211ee1c1f2cd6d6125a33e4240b9af0a9d99ba 100644
--- a/Source/core/svg/SVGElement.cpp
+++ b/Source/core/svg/SVGElement.cpp
@@ -753,11 +753,9 @@ void SVGElement::collectStyleForPresentationAttribute(const QualifiedName& name,
 
 bool SVGElement::haveLoadedRequiredResources()
 {
-    Node* child = firstChild();
-    while (child) {
-        if (child->isSVGElement() && !toSVGElement(child)->haveLoadedRequiredResources())
+    for (SVGElement* child = Traversal<SVGElement>::firstChild(*this); child; child = Traversal<SVGElement>::nextSibling(*child)) {
+        if (!child->haveLoadedRequiredResources())
             return false;
-        child = child->nextSibling();
     }
     return true;
 }