Make collection caching code more consistent

Source/core/html/LabelableElement.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, 2007 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 26 matching lines @@
 
 LabelableElement::~LabelableElement()
 {
 }
 
 PassRefPtrWillBeRawPtr<LabelsNodeList> LabelableElement::labels()
 {
     if (!supportLabels())
         return nullptr;
 
-    return ensureRareData().ensureNodeLists().addCache<LabelsNodeList>(*this, LabelsNodeListType);
+    return ensureCachedCollection<LabelsNodeList>(LabelsNodeListType);
 }
 
 void LabelableElement::trace(Visitor* visitor)
 {
     HTMLElement::trace(visitor);
 }
 
 } // namespace Webcore