This CL clean up patch in SVGElements.

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 113 matching lines @@
     if (!isExternalURIReference(hrefString(), document()))
         return &treeScope();
     return externalDocument();
 }
 
 Document* SVGUseElement::externalDocument() const
 {
     if (m_resource && m_resource->isLoaded()) {
         // Gracefully handle error condition.
         if (m_resource->errorOccurred())
-            return 0;
+            return nullptr;
         ASSERT(m_resource->document());
         return m_resource->document();
     }
-    return 0;
+    return nullptr;
 }
 
 void transferUseWidthAndHeightIfNeeded(const SVGUseElement& use, SVGElement* shadowElement, const SVGElement& originalElement)
 {
     DEFINE_STATIC_LOCAL(const AtomicString, hundredPercentString, ("100%", AtomicString::ConstructFromLiteral));
     ASSERT(shadowElement);
     if (isSVGSymbolElement(*shadowElement)) {
         // Spec (<use> on <symbol>): This generated 'svg' will always have explicit values for attributes width and height.
         // If attributes width and/or height are provided on the 'use' element, then these attributes
         // will be transferred to the generated 'svg'. If attributes width and/or height are not specified,
@@ skipping 309 matching lines @@
     }
 }
 
 LayoutObject* SVGUseElement::layoutObjectClipChild() const
 {
     if (Node* n = userAgentShadowRoot()->firstChild()) {
         if (n->isSVGElement() && isDirectReference(toSVGElement(*n)))
             return n->layoutObject();
     }
 
-    return 0;
+    return nullptr;
 }
 
 bool SVGUseElement::buildShadowTree(SVGElement* target, SVGElement* targetInstance, bool foundUse)
 {
     ASSERT(target);
     ASSERT(targetInstance);
 
     // Spec: If the referenced object is itself a 'use', or if there are 'use' subelements within the referenced
     // object, the instance tree will contain recursive expansion of the indirect references to form a complete tree.
     if (isSVGUseElement(*target)) {
@@ skipping 283 matching lines @@
 
     if (m_resource)
         m_resource->removeClient(this);
 
     m_resource = resource;
     if (m_resource)
         m_resource->addClient(this);
 }
 
 }