Have Element::ensureUserAgentShadowRoot() return a reference

Source/core/html/HTMLKeygenElement.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, 2010 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 32 matching lines @@
 using namespace HTMLNames;
 
 HTMLKeygenElement::HTMLKeygenElement(const QualifiedName& tagName, Document& document, HTMLFormElement* form)
     : HTMLFormControlElementWithState(tagName, document, form)
 {
     ASSERT(hasTagName(keygenTag));
     ScriptWrappable::init(this);
     ensureUserAgentShadowRoot();
 }
 
-void HTMLKeygenElement::didAddUserAgentShadowRoot(ShadowRoot* root)
+void HTMLKeygenElement::didAddUserAgentShadowRoot(ShadowRoot& root)
 {
     DEFINE_STATIC_LOCAL(AtomicString, keygenSelectPseudoId, ("-webkit-keygen-select", AtomicString::ConstructFromLiteral));
 
     Vector<String> keys;
     getSupportedKeySizes(locale(), keys);
 
     // Create a select element with one option element for each key size.
     RefPtr<HTMLSelectElement> select = HTMLSelectElement::create(document());
     select->setPart(keygenSelectPseudoId);
     for (size_t i = 0; i < keys.size(); ++i) {
         RefPtr<HTMLOptionElement> option = HTMLOptionElement::create(document());
         option->appendChild(Text::create(document(), keys[i]));
         select->appendChild(option);
     }
 
-    root->appendChild(select);
+    root.appendChild(select);
 }
 
 void HTMLKeygenElement::parseAttribute(const QualifiedName& name, const AtomicString& value)
 {
     // Reflect disabled attribute on the shadow select element
     if (name == disabledAttr)
         shadowSelect()->setAttribute(name, value);
 
     HTMLFormControlElement::parseAttribute(name, value);
 }
@@ skipping 27 matching lines @@
     ShadowRoot* root = userAgentShadowRoot();
     return root ? toHTMLSelectElement(root->firstChild()) : 0;
 }
 
 bool HTMLKeygenElement::isInteractiveContent() const
 {
     return true;
 }
 
 } // namespace