Introduce toSVGUseElement(), use it

Source/core/svg/SVGStyledElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 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 72 matching lines @@
         return String();
 
     // Walk up the tree, to find out whether we're inside a <use> shadow tree, to find the right title.
     if (isInShadowTree()) {
         Element* shadowHostElement = toShadowRoot(treeScope()->rootNode())->host();
         // At this time, SVG nodes are not allowed in non-<use> shadow trees, so any shadow root we do
         // have should be a use. The assert and following test is here to catch future shadow DOM changes
         // that do enable SVG in a shadow tree.
         ASSERT(!shadowHostElement || shadowHostElement->hasTagName(SVGNames::useTag));
         if (shadowHostElement && shadowHostElement->hasTagName(SVGNames::useTag)) {
-            SVGUseElement* useElement = static_cast<SVGUseElement*>(shadowHostElement);
+            SVGUseElement* useElement = toSVGUseElement(shadowHostElement);
  
             // If the <use> title is not empty we found the title to use.
             String useTitle(useElement->title());
             if (!useTitle.isEmpty())
                return useTitle;
         }
     }
 
     // If we aren't an instance in a <use> or the <use> title was not found, then find the first
     // <title> child of this element.
@@ skipping 372 matching lines @@
     Element* eventTarget = const_cast<SVGStyledElement *>(this);
     return eventTarget->hasEventListeners(eventNames().focusinEvent) || eventTarget->hasEventListeners(eventNames().focusoutEvent);
 }
 
 bool SVGStyledElement::isKeyboardFocusable(KeyboardEvent*) const
 {
     return isMouseFocusable();
 }
 
 }