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

Source/core/css/CSSSelector.h

Index: Source/core/css/CSSSelector.h
diff --git a/Source/core/css/CSSSelector.h b/Source/core/css/CSSSelector.h
index 5d2845a7541c5fffb052927a42bc4a80d7cbb517..5ea949385cfab4f21ecb2d789edd3458843fc2e8 100644
--- a/Source/core/css/CSSSelector.h
+++ b/Source/core/css/CSSSelector.h
@@ -128,11 +128,8 @@ namespace WebCore {
             DirectAdjacent, // + combinator
             IndirectAdjacent, // ~ combinator
             SubSelector, // "No space" combinator
-            ShadowPseudo, // Special case of shadow DOM pseudo elements
-            // FIXME: implement named combinator (i.e. named relation) and
-            // replace the following /shadow/ and /shadow-deep/ with the implementation.
-            Shadow, // /shadow/ combinator
-            ShadowDeep, // /shadow-deep/ combinator
+            ShadowPseudo, // Special case of shadow DOM pseudo elements / shadow pseudo element

[dglazkov, 2014/03/25 17:10:53]

This needs to be renamed to CustomPseudoElement or something, now that we have
an actual shadow pseudo :)

[tasak, 2014/03/26 11:01:46]

The actual shadow pseudo uses this relation, because, for example, div::shadow >
div" is converted to "div <==ShadowPseudo== ::shadow <==Child== div".

SelectorChecker uses "ShadowPseudo" to walk up from "::shadow"(shadow root) to
"div"(shadow host), because shadow roots are not elements.

+            ShadowDeep // /shadow-deep/ combinator
         };
 
         enum PseudoType {
@@ -218,7 +215,8 @@ namespace WebCore {
             PseudoUnresolved,
             PseudoContent,
             PseudoHost,
-            PseudoAncestor
+            PseudoAncestor,
+            PseudoShadow
         };
 
         enum OptionalPseudoTypeRequirements {
@@ -294,6 +292,7 @@ namespace WebCore {
         bool isAttributeSelector() const;
         bool isDistributedPseudoElement() const;
         bool isContentPseudoElement() const;
+        bool isShadowPseudoElement() const;
         bool isHostPseudoClass() const;
 
         // FIXME: selectors with no tagHistory() get a relation() of Descendant. It should instead be
@@ -429,6 +428,11 @@ inline bool CSSSelector::isContentPseudoElement() const
     return m_match == PseudoElement && pseudoType() == PseudoContent;
 }
 
+inline bool CSSSelector::isShadowPseudoElement() const
+{
+    return m_match == PseudoElement && pseudoType() == PseudoShadow;
+}
+
 inline void CSSSelector::setValue(const AtomicString& value)
 {
     ASSERT(m_match != Tag);