Have Document::timeline() / Document::transitionTimeline() return a reference

Source/core/dom/Document.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 983 matching lines @@
     void didRemoveAllPendingStylesheet();
     void setNeedsNotifyRemoveAllPendingStylesheet() { m_needsNotifyRemoveAllPendingStylesheet = true; }
     void clearStyleResolver();
 
     bool inStyleRecalc() const { return m_lifecycle.state() == DocumentLifecycle::InStyleRecalc; }
 
     // Return a Locale for the default locale if the argument is null or empty.
     Locale& getCachedLocale(const AtomicString& locale = nullAtom);
 
     AnimationClock& animationClock() { return *m_animationClock; }
-    DocumentTimeline* timeline() const { return m_timeline.get(); }
-    DocumentTimeline* transitionTimeline() const { return m_transitionTimeline.get(); }
+    DocumentTimeline& timeline() const { return *m_timeline; }
+    DocumentTimeline& transitionTimeline() const { return *m_transitionTimeline; }
     CSSPendingAnimations& cssPendingAnimations() { return m_cssPendingAnimations; }
 
     void addToTopLayer(Element*, const Element* before = 0);
     void removeFromTopLayer(Element*);
     const Vector<RefPtr<Element> >& topLayerElements() const { return m_topLayerElements; }
     HTMLDialogElement* activeModalDialog() const;
 
     // A non-null m_templateDocumentHost implies that |this| was created by ensureTemplateDocument().
     bool isTemplateDocument() const { return !!m_templateDocumentHost; }
     Document& ensureTemplateDocument();
@@ skipping 380 matching lines @@
 inline bool Node::isDocumentNode() const
 {
     return this == document();
 }
 
 Node* eventTargetNodeForDocument(Document*);
 
 } // namespace WebCore
 
 #endif // Document_h