Make a '::distributed' pseudo element the first-ever client who can accept a relative selector.

Source/core/css/CSSParserValues.h

 /*
  * Copyright (C) 2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2008, 2009, 2010 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
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 175 matching lines @@
 
 class CSSParserSelector {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     CSSParserSelector();
     explicit CSSParserSelector(const QualifiedName&);
     ~CSSParserSelector();
 
     PassOwnPtr<CSSSelector> releaseSelector() { return m_selector.release(); }
 
+    CSSSelector::Relation relation() const { return m_selector->relation(); }
     void setValue(const AtomicString& value) { m_selector->setValue(value); }
     void setAttribute(const QualifiedName& value) { m_selector->setAttribute(value); }
     void setArgument(const AtomicString& value) { m_selector->setArgument(value); }
     void setMatch(CSSSelector::Match value) { m_selector->m_match = value; }
     void setRelation(CSSSelector::Relation value) { m_selector->m_relation = value; }
     void setForPage() { m_selector->setForPage(); }
 
     void adoptSelectorVector(Vector<OwnPtr<CSSParserSelector> >& selectorVector);
 
     CSSParserSelector* functionArgumentSelector() const { return m_functionArgumentSelector; }
@@ skipping 21 matching lines @@
 };
 
 inline bool CSSParserSelector::hasShadowPseudo() const
 {
     return m_selector->relation() == CSSSelector::ShadowPseudo;
 }
 
 }
 
 #endif