Have Element::ensureUserAgentShadowRoot() return a reference

Source/core/html/HTMLInputElement.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, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Samsung Electronics. 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
@@ skipping 269 matching lines @@
     bool supportsInputModeAttribute() const;
 
 protected:
     HTMLInputElement(const QualifiedName&, Document&, HTMLFormElement*, bool createdByParser);
 
     virtual void defaultEventHandler(Event*);
 
 private:
     enum AutoCompleteSetting { Uninitialized, On, Off };
 
-    virtual void didAddUserAgentShadowRoot(ShadowRoot*) OVERRIDE;
+    virtual void didAddUserAgentShadowRoot(ShadowRoot&) OVERRIDE;
     virtual void didAddShadowRoot(ShadowRoot&) OVERRIDE;
 
     virtual void willChangeForm() OVERRIDE;
     virtual void didChangeForm() OVERRIDE;
     virtual InsertionNotificationRequest insertedInto(ContainerNode*) OVERRIDE;
     virtual void removedFrom(ContainerNode*) OVERRIDE;
     virtual void didMoveToNewDocument(Document& oldDocument) OVERRIDE;
 
     virtual bool hasCustomFocusLogic() const OVERRIDE;
     virtual bool isKeyboardFocusable() const OVERRIDE;
@@ skipping 102 matching lines @@
     // that it lives as long as its owning element lives. If we move the loader into
     // the ImageInput object we may delete the loader while this element lives on.
     OwnPtr<HTMLImageLoader> m_imageLoader;
     OwnPtr<ListAttributeTargetObserver> m_listAttributeTargetObserver;
 };
 
 DEFINE_NODE_TYPE_CASTS(HTMLInputElement, hasTagName(HTMLNames::inputTag));
 
 } //namespace
 #endif