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

Source/core/dom/SelectorQuery.cpp

Index: Source/core/dom/SelectorQuery.cpp
diff --git a/Source/core/dom/SelectorQuery.cpp b/Source/core/dom/SelectorQuery.cpp
index 4628803bb2f2fca2f566477f1583b88e72460066..df39a559e8a7aafff358f9fee28cd45b1f9ed5a2 100644
--- a/Source/core/dom/SelectorQuery.cpp
+++ b/Source/core/dom/SelectorQuery.cpp
@@ -110,7 +110,7 @@ void SelectorDataList::initialize(const CSSSelectorList& selectorList)
     unsigned index = 0;
     for (const CSSSelector* selector = selectorList.first(); selector; selector = CSSSelectorList::next(*selector), ++index) {
         m_selectors.uncheckedAppend(selector);
-        m_crossesTreeBoundary |= selectorList.hasCombinatorCrossingTreeBoundaryAt(index);
+        m_crossesTreeBoundary |= selectorList.selectorCrossesTreeScopes(index);
     }
 }