Revert "Reverting custom pseudo element".

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 386 matching lines @@
     void setOuterHTML(const String&, ExceptionState&);
 
     Element* insertAdjacentElement(const String& where, Element* newChild, ExceptionState&);
     void insertAdjacentText(const String& where, const String& text, ExceptionState&);
     void insertAdjacentHTML(const String& where, const String& html, ExceptionState&);
 
     String textFromChildren();
 
     virtual String title() const { return String(); }
 
+    virtual const AtomicString& pseudo() const { return shadowPseudoId(); }
+    void setPseudo(const AtomicString& value) { setShadowPseudoId(value); }
     virtual const AtomicString& shadowPseudoId() const;
     void setShadowPseudoId(const AtomicString&);
 
     LayoutSize minimumSizeForResizing() const;
     void setMinimumSizeForResizing(const LayoutSize&);
 
     virtual void didBecomeFullscreenElement() { }
     virtual void willStopBeingFullscreenElement() { }
 
     using Node::isFinishedParsingChildren; // make public for SelectorChecker
@@ skipping 442 matching lines @@
 }
 
 inline bool isShadowHost(const Element* element)
 {
     return element && element->shadow();
 }
 
 } // namespace
 
 #endif