Handle ::content and :host-context correctly in SelectorQuery.

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 177 matching lines @@
         return selector.relation() == CSSSelector::ShadowDeep || selector.isShadowPseudoElement();
     }
 };
 
 bool CSSSelectorList::selectorCrossesTreeScopes(size_t index) const
 {
     SelectorCrossesTreeScopes functor;
     return forEachTagSelector(functor, selectorAt(index));
 }
 
+class SelectorNeedsUpdatedDistribution {
+public:
+    bool operator()(const CSSSelector& selector)
+    {
+        return selector.relationIsAffectedByPseudoContent() || selector.pseudoType() == CSSSelector::PseudoHostContext;
+    }
+};
+
+bool CSSSelectorList::selectorNeedsUpdatedDistribution(size_t index) const
+{
+    SelectorNeedsUpdatedDistribution functor;
+    return forEachTagSelector(functor, selectorAt(index));
+}
+
 } // namespace blink