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

Source/core/css/RuleFeature.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 33 matching lines @@
 {
     if (selector.m_match == CSSSelector::Tag
         || selector.m_match == CSSSelector::Id
         || selector.isAttributeSelector())
         return true;
     if (selector.m_match == CSSSelector::PseudoElement) {
         switch (selector.m_pseudoType) {
         case CSSSelector::PseudoBefore:
         case CSSSelector::PseudoAfter:
         case CSSSelector::PseudoBackdrop:
+        case CSSSelector::PseudoShadow:
             return true;
         default:
             return false;
         }
     }
     if (selector.m_match != CSSSelector::PseudoClass)
         return false;
     switch (selector.pseudoType()) {
     case CSSSelector::PseudoEmpty:
     case CSSSelector::PseudoFirstChild:
@@ skipping 47 matching lines @@
         // FIXME: next up: Tag and Id.
         if (component->m_match == CSSSelector::Class || component->isAttributeSelector()) {
             if (!foundDescendantRelation)
                 foundIdent = true;
         } else if (!isSkippableComponentForInvalidation(*component)) {
             return foundDescendantRelation ? UseLocalStyleChange : UseSubtreeStyleChange;
         }
         switch (component->relation()) {
         case CSSSelector::Descendant:
         case CSSSelector::Child:
-        case CSSSelector::Shadow:
+        case CSSSelector::ShadowPseudo:
         case CSSSelector::ShadowDeep:
             foundDescendantRelation = true;
             // Fall through!
         case CSSSelector::SubSelector:
             continue;
         default:
             return UseLocalStyleChange;
         }
     }
     return foundIdent ? AddFeatures : UseLocalStyleChange;
@@ skipping 261 matching lines @@
     if (node->isElementNode())
         m_pendingInvalidationMap.remove(toElement(node));
 }
 
 RuleFeatureSet::PendingInvalidationMap& RuleFeatureSet::pendingInvalidationMap()
 {
     return m_pendingInvalidationMap;
 }
 
 } // namespace WebCore