Use isSVG*Element() helpers more in SVG code (Part 1)

Source/core/svg/SVGDocument.cpp

 /*
  * Copyright (C) 2004, 2005 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007 Rob Buis <buis@kde.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 24 matching lines @@
 namespace WebCore {
 
 SVGDocument::SVGDocument(const DocumentInit& initializer)
     : XMLDocument(initializer, XMLDocumentClass | SVGDocumentClass)
 {
 }
 
 SVGSVGElement* SVGDocument::rootElement(const Document& document)
 {
     Element* elem = document.documentElement();
-    if (elem && elem->hasTagName(SVGNames::svgTag))
-        return toSVGSVGElement(elem);
-
-    return 0;
+    return isSVGSVGElement(elem) ? toSVGSVGElement(elem) : 0;
 }
 
 SVGSVGElement* SVGDocument::rootElement() const
 {
     return rootElement(*this);
 }
 
 void SVGDocument::dispatchZoomEvent(float prevScale, float newScale)
 {
     RefPtr<SVGZoomEvent> event = SVGZoomEvent::create();
@@ skipping 38 matching lines @@
             renderer()->repaint();
     }
 }
 
 PassRefPtr<Document> SVGDocument::cloneDocumentWithoutChildren()
 {
     return create(DocumentInit(url()));
 }
 
 }