Have Node::highestAncestor() return a reference

Source/core/html/FormAssociatedElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * 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
@@ skipping 102 matching lines @@
         if (newFormCandidate && newFormCandidate->hasTagName(formTag))
             newForm = toHTMLFormElement(newFormCandidate);
         return newForm;
     }
     // 4. Otherwise, if the form-associated element in question has an ancestor
     // form element, then associate the form-associated element with the nearest
     // such ancestor form element.
     return element->findFormAncestor();
 }
 
-void FormAssociatedElement::formRemovedFromTree(const Node* formRoot)
+void FormAssociatedElement::formRemovedFromTree(const Node& formRoot)
 {
     ASSERT(m_form);
     if (toHTMLElement(this)->highestAncestor() == formRoot)
         return;
     resetFormOwner();
 }
 
 void FormAssociatedElement::associateByParser(HTMLFormElement* form)
 {
     if (form && form->inDocument()) {
@@ skipping 182 matching lines @@
     , m_element(element)
 {
 }
 
 void FormAttributeTargetObserver::idTargetChanged()
 {
     m_element->formAttributeTargetChanged();
 }
 
 } // namespace Webcore