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

Source/core/css/CSSGrammar.y

 %{
 
 /*
  *  Copyright (C) 2002-2003 Lars Knoll (knoll@kde.org)
  *  Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  *  Copyright (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *  Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  *  Copyright (C) 2012 Intel Corporation. All rights reserved.
  *
  *  This library is free software; you can redistribute it and/or
@@ skipping 1028 matching lines @@
     '{' at_rule_body_start maybe_space_before_declaration declaration_list closing_brace {
         $$ = parser->createViewportRule();
         parser->markViewportRuleBodyEnd();
     }
 ;
 
 combinator:
     '+' maybe_space { $$ = CSSSelector::DirectAdjacent; }
     | '~' maybe_space { $$ = CSSSelector::IndirectAdjacent; }
     | '>' maybe_space { $$ = CSSSelector::Child; }
-    // FIXME: implement named combinator and replace the following /shadow/, /shadow-child/ and
-    // /shadow-deep/ with named combinator's implementation.
     | '/' IDENT '/' maybe_space {
-        if ($2.equalIgnoringCase("shadow"))
-            $$ = CSSSelector::Shadow;
-        else if ($2.equalIgnoringCase("shadow-deep"))
+        if ($2.equalIgnoringCase("shadow-deep"))
             $$ = CSSSelector::ShadowDeep;
         else
             YYERROR;
     }
     ;
 
 maybe_unary_operator:
     unary_operator
     | /* empty */ { $$ = 1; }
     ;
@@ skipping 831 matching lines @@
     ;
 
 rule_error_recovery:
     /* empty */
   | rule_error_recovery error
   | rule_error_recovery invalid_square_brackets_block
   | rule_error_recovery invalid_parentheses_block
     ;
 
 %%