Implement ::shadow pseudo element and replace /shadow/ with ::shadow.

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 bef8f1ef7259811e3292378d1d1f42838e2d2eb8..16b1bc2396db4b86c091e48d9c447df996e68d1a 100644
--- a/Source/core/css/CSSSelectorList.cpp
+++ b/Source/core/css/CSSSelectorList.cpp
@@ -182,17 +182,17 @@ bool CSSSelectorList::hasShadowDistributedAt(size_t index) const
     return forEachTagSelector(functor, selectorAt(index));
 }
 
-class SelectorHasCombinatorCrossingTreeBoundary {
+class SelectorCrossesTreeScopes {
 public:
     bool operator()(const CSSSelector& selector)
     {
-        return selector.relation() == CSSSelector::Shadow || selector.relation() == CSSSelector::ShadowDeep;
+        return selector.relation() == CSSSelector::ShadowDeep || selector.isShadowPseudoElement();
     }
 };
 
-bool CSSSelectorList::hasCombinatorCrossingTreeBoundaryAt(size_t index) const
+bool CSSSelectorList::selectorCrossesTreeScopes(size_t index) const
 {
-    SelectorHasCombinatorCrossingTreeBoundary functor;
+    SelectorCrossesTreeScopes functor;
     return forEachTagSelector(functor, selectorAt(index));
 }