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

Source/core/css/CSSSelectorList.cpp

Index: Source/core/css/CSSSelectorList.cpp
diff --git a/Source/core/css/CSSSelectorList.cpp b/Source/core/css/CSSSelectorList.cpp
index ab96e144bb2752f258cf5f603d34143ed0d1ac1c..b51944e7877d077ba2b712c9119d9f12442ed6c6 100644
--- a/Source/core/css/CSSSelectorList.cpp
+++ b/Source/core/css/CSSSelectorList.cpp
@@ -195,4 +195,18 @@ bool CSSSelectorList::selectorCrossesTreeScopes(size_t index) const
     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