Revert "Implement proposed shadow tree cascade order."

Source/core/dom/DocumentOrderedList.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) 2013 Google Inc. All rights reserved.
  *
@@ skipping 32 matching lines @@
     DocumentOrderedList() { }
 
     void add(Node*);
     void parserAdd(Node*);
     void remove(const Node*);
     bool isEmpty() const { return m_nodes.isEmpty(); }
     void clear() { m_nodes.clear(); }
     size_t size() const { return m_nodes.size(); }
 
     using iterator = WillBeHeapListHashSet<RawPtrWillBeMember<Node>, 32>::iterator;
-    using const_reverse_iterator = WillBeHeapListHashSet<RawPtrWillBeMember<Node>, 32>::const_reverse_iterator;
 
     iterator begin() { return m_nodes.begin(); }
     iterator end() { return m_nodes.end(); }
 
-    const_reverse_iterator rbegin() const { return m_nodes.rbegin(); }
-    const_reverse_iterator rend() const { return m_nodes.rend(); }
-
     DECLARE_TRACE();
 
 private:
     WillBeHeapListHashSet<RawPtrWillBeMember<Node>, 32> m_nodes;
 };
 
 }
 
 #endif