Reduce forward declarations in core/svg

Source/core/svg/SVGURIReference.h

 /*
  * Copyright (C) 2004, 2005, 2008, 2009 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005 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,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #ifndef SVGURIReference_h
 #define SVGURIReference_h
 
 #include "core/dom/Document.h"
 #include "core/svg/SVGAnimatedString.h"
 
 namespace WebCore {
 
-class Attribute;
 class Element;
 
 class SVGURIReference {
 public:
     virtual ~SVGURIReference() { }
 
     bool isKnownAttribute(const QualifiedName&);
     void addSupportedAttributes(HashSet<QualifiedName>&);
 
     static AtomicString fragmentIdentifierFromIRIString(const String&, const TreeScope&);
@@ skipping 19 matching lines @@
 protected:
     explicit SVGURIReference(SVGElement*);
 
 private:
     RefPtr<SVGAnimatedString> m_href;
 };
 
 } // namespace WebCore
 
 #endif // SVGURIReference_h