Have Node::highestAncestor() return a reference

Source/core/html/HTMLFormElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 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.
@@ skipping 121 matching lines @@
 
     virtual bool shouldRegisterAsNamedItem() const OVERRIDE { return true; }
 
     virtual void copyNonAttributePropertiesFromElement(const Element&) OVERRIDE;
 
     void submitDialog(PassRefPtr<FormSubmission>);
     void submit(Event*, bool activateSubmitButton, bool processingUserGesture, FormSubmissionTrigger);
 
     void scheduleFormSubmission(PassRefPtr<FormSubmission>);
 
-    void collectAssociatedElements(Node* root, Vector<FormAssociatedElement*>&) const;
-    void collectImageElements(Node* root, Vector<HTMLImageElement*>&);
+    void collectAssociatedElements(Node& root, Vector<FormAssociatedElement*>&) const;
+    void collectImageElements(Node& root, Vector<HTMLImageElement*>&);
 
     // Returns true if the submission should proceed.
     bool validateInteractively(Event*);
 
     // Validates each of the controls, and stores controls of which 'invalid'
     // event was not canceled to the specified vector. Returns true if there
     // are any invalid controls in this form.
     bool checkInvalidControlsAndCollectUnhandled(Vector<RefPtr<FormAssociatedElement> >*, HTMLFormControlElement::CheckValidityDispatchEvents = HTMLFormControlElement::CheckValidityDispatchEventsAllowed);
 
     Element* elementFromPastNamesMap(const AtomicString&);
@@ skipping 27 matching lines @@
 
     void requestAutocompleteTimerFired(Timer<HTMLFormElement>*);
 
     Vector<RefPtr<Event> > m_pendingAutocompleteEvents;
     Timer<HTMLFormElement> m_requestAutocompleteTimer;
 };
 
 } // namespace WebCore
 
 #endif // HTMLFormElement_h