Remove ::part.

Source/core/css/CSSGrammar.y

Index: Source/core/css/CSSGrammar.y
diff --git a/Source/core/css/CSSGrammar.y b/Source/core/css/CSSGrammar.y
index 57152309e61b73cbf73d86514e74e8a840a37744..925ae5060d84a5382fb5ee8d6ab24041b8dd6cce 100644
--- a/Source/core/css/CSSGrammar.y
+++ b/Source/core/css/CSSGrammar.y
@@ -261,7 +261,6 @@ inline static CSSParserValue makeOperatorValue(int value)
 %token <string> MAXFUNCTION
 %token <string> VARFUNCTION
 %token <string> VAR_DEFINITION
-%token <string> PARTFUNCTION
 %token <string> HOSTFUNCTION
 
 %token <string> UNICODERANGE
@@ -1552,21 +1551,6 @@ pseudo:
     | ':' NOTFUNCTION selector_recovery closing_parenthesis {
         YYERROR;
     }
-    | ':' ':' PARTFUNCTION maybe_space IDENT maybe_space closing_parenthesis {
-        $$ = parser->createFloatingSelector();
-        $$->setMatch(CSSSelector::PseudoElement);
-        $$->setArgument($5);
-        if ($5.startsWithIgnoringCase("-webkit"))
-            $$->setMatchUserAgentOnly();
-        parser->tokenToLowerCase($3);
-        $$->setValue($3);
-        CSSSelector::PseudoType type = $$->pseudoType();
-        if (type != CSSSelector::PseudoPart)
-            YYERROR;
-    }
-    | ':' ':' PARTFUNCTION selector_recovery closing_parenthesis {
-        YYERROR;
-    }
     | ':' HOSTFUNCTION maybe_space simple_selector_list maybe_space closing_parenthesis {
         $$ = parser->createFloatingSelector();
         $$->setMatch(CSSSelector::PseudoClass);