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

Source/core/css/CSSSelectorList.cpp

 /*
  * Copyright (C) 2008, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 172 matching lines @@
 bool CSSSelectorList::hasInvalidSelector() const
 {
     SelectorHasInvalidSelectorFunctor functor;
     return forEachSelector(functor, this);
 }
 
 class SelectorHasShadowDistributed {
 public:
     bool operator()(const CSSSelector* selector)
     {
-        return selector->isShadowDistributed();
+        return selector->relationIsForShadowDistributed();
     }
 };
 
 bool CSSSelectorList::hasShadowDistributedAt(size_t index) const
 {
     SelectorHasShadowDistributed functor;
     return forEachTagSelector(functor, selectorAt(index));
 }
 
 } // namespace WebCore