Introduce toSVGFontFaceElement, and use it

Source/core/svg/SVGFontFaceUriElement.cpp

 /*
  * Copyright (C) 2007 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * 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 61 matching lines @@
 
 void SVGFontFaceUriElement::childrenChanged(bool changedByParser, Node* beforeChange, Node* afterChange, int childCountDelta)
 {
     SVGElement::childrenChanged(changedByParser, beforeChange, afterChange, childCountDelta);
 
     if (!parentNode() || !parentNode()->hasTagName(font_face_srcTag))
         return;
 
     ContainerNode* grandparent = parentNode()->parentNode();
     if (grandparent && grandparent->hasTagName(font_faceTag))
-        static_cast<SVGFontFaceElement*>(grandparent)->rebuildFontFace();
+        toSVGFontFaceElement(grandparent)->rebuildFontFace();
 }
 
 Node::InsertionNotificationRequest SVGFontFaceUriElement::insertedInto(ContainerNode* rootParent)
 {
     loadFont();
     return SVGElement::insertedInto(rootParent);
 }
 
 void SVGFontFaceUriElement::loadFont()
 {
     if (m_cachedFont)
         m_cachedFont->removeClient(this);
 
     const AtomicString& href = getAttribute(XLinkNames::hrefAttr);
     if (!href.isNull()) {
         ResourceFetcher* fetcher = document()->fetcher();
         FetchRequest request(ResourceRequest(document()->completeURL(href)), localName());
         m_cachedFont = fetcher->requestFont(request);
         if (m_cachedFont) {
             m_cachedFont->addClient(this);
             m_cachedFont->beginLoadIfNeeded(fetcher);
         }
     } else
         m_cachedFont = 0;
 }
 
 }
 
 #endif // ENABLE(SVG_FONTS)