Add toSVGForeignObjectElement(), and use it.

Source/core/svg/SVGForeignObjectElement.h

 /*
  * Copyright (C) 2006 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,
  * 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 SVGForeignObjectElement_h
 #define SVGForeignObjectElement_h
 
+#include "SVGNames.h"
 #include "core/svg/SVGAnimatedBoolean.h"
 #include "core/svg/SVGAnimatedLength.h"
 #include "core/svg/SVGExternalResourcesRequired.h"
 #include "core/svg/SVGGraphicsElement.h"
 #include "core/svg/SVGURIReference.h"
 
 namespace WebCore {
 
 class SVGForeignObjectElement FINAL : public SVGGraphicsElement,
                                       public SVGExternalResourcesRequired {
@@ skipping 17 matching lines @@
     BEGIN_DECLARE_ANIMATED_PROPERTIES(SVGForeignObjectElement)
         DECLARE_ANIMATED_LENGTH(X, x)
         DECLARE_ANIMATED_LENGTH(Y, y)
         DECLARE_ANIMATED_LENGTH(Width, width)
         DECLARE_ANIMATED_LENGTH(Height, height)
         DECLARE_ANIMATED_STRING(Href, href)
         DECLARE_ANIMATED_BOOLEAN(ExternalResourcesRequired, externalResourcesRequired)
     END_DECLARE_ANIMATED_PROPERTIES
 };
 
+inline SVGForeignObjectElement* toSVGForeignObjectElement(Node* node)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!node || node->hasTagName(SVGNames::foreignObjectTag));
+    return static_cast<SVGForeignObjectElement*>(node);
+}
+
 } // namespace WebCore
 
 #endif