Have LiveNodeListBase::ownerNode() return a reference

Source/core/html/HTMLCollection.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2014 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
  * version 2 of the License, or (at your option) any later version.
@@ skipping 163 matching lines @@
     return adoptRef(new HTMLCollection(base, type, DoesNotOverrideItemAfter));
 }
 
 HTMLCollection::~HTMLCollection()
 {
     if (hasValidIdNameCache())
         unregisterIdNameCacheFromDocument(document());
     // HTMLNameCollection, ClassCollection and TagCollection remove cache by themselves.
     if (type() != WindowNamedItems && type() != DocumentNamedItems && type() != ClassCollectionType
         && type() != HTMLTagCollectionType && type() != TagCollectionType) {
-        ownerNode()->nodeLists()->removeCache(this, type());
+        ownerNode().nodeLists()->removeCache(this, type());
     }
 }
 
 void HTMLCollection::invalidateCache(Document* oldDocument) const
 {
     m_collectionIndexCache.invalidate();
     invalidateIdNameCacheMaps(oldDocument);
 }
 
 template <class NodeListType>
@@ skipping 340 matching lines @@
 
 void HTMLCollection::append(NodeCacheMap& map, const AtomicString& key, Element* element)
 {
     OwnPtr<Vector<Element*> >& vector = map.add(key.impl(), nullptr).storedValue->value;
     if (!vector)
         vector = adoptPtr(new Vector<Element*>);
     vector->append(element);
 }
 
 } // namespace WebCore