Have Element::ensureUserAgentShadowRoot() return a reference

Source/core/dom/Element.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2013 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
@@ skipping 295 matching lines @@
 
     ElementShadow* shadow() const;
     ElementShadow& ensureShadow();
     PassRefPtr<ShadowRoot> createShadowRoot(ExceptionState&);
     ShadowRoot* shadowRoot() const;
     ShadowRoot* youngestShadowRoot() const;
 
     bool hasAuthorShadowRoot() const { return shadowRoot(); }
     virtual void didAddShadowRoot(ShadowRoot&);
     ShadowRoot* userAgentShadowRoot() const;
-    ShadowRoot* ensureUserAgentShadowRoot();
+    ShadowRoot& ensureUserAgentShadowRoot();
     const AtomicString& shadowPseudoId() const;
 
     RenderStyle* computedStyle(PseudoId = NOPSEUDO);
 
     // Methods for indicating the style is affected by dynamic updates (e.g., children changing, our position changing in our sibling list, etc.)
     bool styleAffectedByEmpty() const { return hasRareData() && rareDataStyleAffectedByEmpty(); }
     bool childrenAffectedByFocus() const { return hasRareData() && rareDataChildrenAffectedByFocus(); }
     bool childrenAffectedByHover() const { return hasRareData() && rareDataChildrenAffectedByHover(); }
     bool childrenAffectedByActive() const { return hasRareData() && rareDataChildrenAffectedByActive(); }
     bool childrenAffectedByDrag() const { return hasRareData() && rareDataChildrenAffectedByDrag(); }
@@ skipping 244 matching lines @@
     void checkForChildrenAdjacentRuleChanges();
 
     void updatePseudoElement(PseudoId, StyleRecalcChange);
 
     inline void createPseudoElementIfNeeded(PseudoId);
     inline bool needsPseudoElement(PseudoId) const;
     void createPseudoElement(PseudoId);
 
     // FIXME: Everyone should allow author shadows.
     virtual bool areAuthorShadowsAllowed() const { return true; }
-    virtual void didAddUserAgentShadowRoot(ShadowRoot*) { }
+    virtual void didAddUserAgentShadowRoot(ShadowRoot&) { }
     virtual bool alwaysCreateUserAgentShadowRoot() const { return false; }
 
     // FIXME: Remove the need for Attr to call willModifyAttribute/didModifyAttribute.
     friend class Attr;
 
     enum SynchronizationOfLazyAttribute { NotInSynchronizationOfLazyAttribute = 0, InSynchronizationOfLazyAttribute };
 
     void didAddAttribute(const QualifiedName&, const AtomicString&);
     void willModifyAttribute(const QualifiedName&, const AtomicString& oldValue, const AtomicString& newValue);
     void didModifyAttribute(const QualifiedName&, const AtomicString&);
@@ skipping 275 matching lines @@
 }
 
 inline bool isShadowHost(const Element* element)
 {
     return element && element->shadow();
 }
 
 } // namespace
 
 #endif