Reduce repetitive EventTarget subclassing

Source/core/svg/SVGElementInstance.cpp

 /*
  * Copyright (C) 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  * Copyright (C) 2011 Torch Mobile (Beijing) Co. Ltd. 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.
  *
@@ skipping 230 matching lines @@
 
     return element->dispatchEvent(event);
 }
 
 EventTargetData* SVGElementInstance::eventTargetData()
 {
     // Since no event listeners are added to an SVGElementInstance, we don't have eventTargetData.
     return 0;
 }
 
-EventTargetData* SVGElementInstance::ensureEventTargetData()
+EventTargetData& SVGElementInstance::ensureEventTargetData()
 {
     // EventTarget would use these methods if we were actually using its add/removeEventListener logic.
     // As we're forwarding those calls to the correspondingElement(), no one should ever call this function.
     ASSERT_NOT_REACHED();
-    return 0;
+    return *eventTargetData();
 }
 
 SVGElementInstance::InstanceUpdateBlocker::InstanceUpdateBlocker(SVGElement* targetElement)
     : m_targetElement(targetElement)
 {
     if (m_targetElement)
         m_targetElement->setInstanceUpdatesBlocked(true);
 }
 
 SVGElementInstance::InstanceUpdateBlocker::~InstanceUpdateBlocker()
 {
     if (m_targetElement)
         m_targetElement->setInstanceUpdatesBlocked(false);
 }
 
 }