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

Source/core/svg/SVGUseElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007 Rob Buis <buis@kde.org>
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  * Copyright (C) 2011 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  * Copyright (C) 2012 University of Szeged
  * Copyright (C) 2012 Renata Hodovan <reni@webkit.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 562 matching lines @@
         return;
     }
 
     // A general description from the SVG spec, describing what buildInstanceTree() actually does.
     //
     // Spec: If the 'use' element references a 'g' which contains two 'rect' elements, then the instance tree
     // contains three SVGElementInstance objects, a root SVGElementInstance object whose correspondingElement
     // is the SVGGElement object for the 'g', and then two child SVGElementInstance objects, each of which has
     // its correspondingElement that is an SVGRectElement object.
 
-    for (Node* node = target->firstChild(); node; node = node->nextSibling()) {
-        SVGElement* element = 0;
-        if (node->isSVGElement())
-            element = toSVGElement(node);
-
-        // Skip any non-svg nodes or any disallowed element.
-        if (!element || isDisallowedElement(element))
+    for (SVGElement* element = Traversal<SVGElement>::firstChild(*target); element; element = Traversal<SVGElement>::nextSibling(*element)) {
+        // Skip any disallowed element.
+        if (isDisallowedElement(element))
             continue;
 
         // Create SVGElementInstance object, for both container/non-container nodes.
         RefPtr<SVGElementInstance> instance = SVGElementInstance::create(this, 0, element);
         SVGElementInstance* instancePtr = instance.get();
         targetInstance->appendChild(instance.release());
 
         // Enter recursion, appending new instance tree nodes to the "instance" object.
         buildInstanceTree(element, instancePtr, foundProblem, foundUse);
         if (foundProblem)
@@ skipping 213 matching lines @@
     }
 
     SVGElement* element = 0;
     if (target->isSVGElement())
         element = toSVGElement(target);
 
     ASSERT(!targetInstance->shadowTreeElement());
     targetInstance->setShadowTreeElement(element);
     element->setCorrespondingElement(originalElement);
 
-    Node* node = target->firstChild();
-    for (SVGElementInstance* instance = targetInstance->firstChild(); node && instance; instance = instance->nextSibling()) {
-        // Skip any non-svg elements in shadow tree
-        while (node && !node->isSVGElement())
-           node = node->nextSibling();
-
-        if (!node)
-            break;
-
-        associateInstancesWithShadowTreeElements(node, instance);
-        node = node->nextSibling();
+    SVGElement* child = Traversal<SVGElement>::firstChild(*target);
+    for (SVGElementInstance* instance = targetInstance->firstChild(); child && instance; instance = instance->nextSibling()) {
+        associateInstancesWithShadowTreeElements(child, instance);
+        child = Traversal<SVGElement>::nextSibling(*child);
     }
 }
 
 SVGElementInstance* SVGUseElement::instanceForShadowTreeElement(Node* element) const
 {
     if (!m_targetElementInstance) {
         ASSERT(!inDocument());
         return 0;
     }
 
@@ skipping 130 matching lines @@
 
     if (m_resource)
         m_resource->removeClient(this);
 
     m_resource = resource;
     if (m_resource)
         m_resource->addClient(this);
 }
 
 }