Have Element::ensureUserAgentShadowRoot() return a reference

Source/core/html/HTMLDetailsElement.cpp

 /*
  * Copyright (C) 2010, 2011 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 36 matching lines @@
 {
     ASSERT(hasTagName(detailsTag));
     ScriptWrappable::init(this);
 }
 
 RenderObject* HTMLDetailsElement::createRenderer(RenderStyle*)
 {
     return new RenderBlockFlow(this);
 }
 
-void HTMLDetailsElement::didAddUserAgentShadowRoot(ShadowRoot* root)
+void HTMLDetailsElement::didAddUserAgentShadowRoot(ShadowRoot& root)
 {
     DEFINE_STATIC_LOCAL(AtomicString, summarySelector, ("summary:first-of-type", AtomicString::ConstructFromLiteral));
 
     RefPtr<HTMLSummaryElement> defaultSummary = HTMLSummaryElement::create(summaryTag, document());
     defaultSummary->appendChild(Text::create(document(), locale().queryString(blink::WebLocalizedString::DetailsLabel)));
 
     RefPtr<HTMLContentElement> content = HTMLContentElement::create(document());
     content->setAttribute(selectAttr, summarySelector);
     content->appendChild(defaultSummary);
 
-    root->appendChild(content);
-    root->appendChild(HTMLContentElement::create(document()));
+    root.appendChild(content);
+    root.appendChild(HTMLContentElement::create(document()));
 }
 
 Element* HTMLDetailsElement::findMainSummary() const
 {
     for (Node* child = firstChild(); child; child = child->nextSibling()) {
         if (child->hasTagName(summaryTag))
             return toElement(child);
     }
 
     HTMLContentElement* content = toHTMLContentElement(userAgentShadowRoot()->firstChild());
@@ skipping 26 matching lines @@
 {
     setAttribute(openAttr, m_isOpen ? nullAtom : emptyAtom);
 }
 
 bool HTMLDetailsElement::isInteractiveContent() const
 {
     return true;
 }
 
 }