Drop empty list :host() and :host-context().

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 c5901b87d0e14ba83fab2ad64b725f9f0c6ab4b5..c88026806e621a1d73b80a2c5a6f1b9455d76aad 100644
--- a/Source/core/css/CSSGrammar.y
+++ b/Source/core/css/CSSGrammar.y
@@ -1468,16 +1468,6 @@ pseudo:
         if (type != CSSSelector::PseudoHost)
             YYERROR;
     }
-    //  used by :host()
-    | ':' HOSTFUNCTION maybe_space closing_parenthesis {
-        $$ = parser->createFloatingSelector();
-        $$->setMatch(CSSSelector::PseudoClass);
-        parser->tokenToLowerCase($2);
-        $$->setValue($2.atomicSubstring(0, $2.length() - 1));
-        CSSSelector::PseudoType type = $$->pseudoType();
-        if (type != CSSSelector::PseudoHost)
-            YYERROR;
-    }
     | ':' HOSTFUNCTION selector_recovery closing_parenthesis {
         YYERROR;
     }
@@ -1492,15 +1482,6 @@ pseudo:
         if (type != CSSSelector::PseudoHostContext)
             YYERROR;
     }
-    | ':' HOSTCONTEXTFUNCTION maybe_space closing_parenthesis {
-        $$ = parser->createFloatingSelector();
-        $$->setMatch(CSSSelector::PseudoClass);
-        parser->tokenToLowerCase($2);
-        $$->setValue($2.atomicSubstring(0, $2.length() - 1));
-        CSSSelector::PseudoType type = $$->pseudoType();
-        if (type != CSSSelector::PseudoHostContext)
-            YYERROR;
-    }
     | ':' HOSTCONTEXTFUNCTION selector_recovery closing_parenthesis {
         YYERROR;
     }