Use isSVG*Element() helpers more in SVG code (Part 4)

Source/core/svg/SVGTextPositioningElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 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 111 matching lines @@
     if (!renderer)
         return 0;
 
     if (!renderer->isSVGText() && !renderer->isSVGInline())
         return 0;
 
     Node* node = renderer->node();
     ASSERT(node);
     ASSERT(node->isSVGElement());
 
-    if (!node->hasTagName(SVGNames::textTag)
-#if ENABLE(SVG_FONTS)
-        && !node->hasTagName(SVGNames::altGlyphTag)
-#endif
-        && !node->hasTagName(SVGNames::tspanTag))
-        return 0;
-
-    return toSVGTextPositioningElement(node);
+    return isSVGTextPositioningElement(*node) ? toSVGTextPositioningElement(node) : 0;
 }
 
 }