Fix enum_syntax_test for dart2js.

tests/language/enum_syntax_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // SharedOptions=--enable-enum
 
 // Basic syntax test for enumeration types
 
 import 'package:expect/expect.dart';
 
@@ skipping 34 matching lines @@
 
 var zzTop;
 enum zzTop { Billy, Dusty, Frank }  /// 11: compile-time error
 
 // Enum type cannot be super type or interface type.
 class Rainbow extends Color {}  /// 20: compile-time error
 class Rainbow implements Color {}  /// 21: compile-time error
 class Rainbow extends List with Color {}  /// 22: compile-time error
 
 main() {
+  Nada x; /// 01: continued
   var x = ComeAgain.zipfel;  /// 02: continued
   var x = ComeAgain.zipfel;  /// 03: continued
   var x = ComeAgain.zipfel;  /// 04: continued
   var x = ComeAgain.zipfel;  /// 05: continued
   var x = ComeAgain.zipfel;  /// 06: continued
   var x = Numbers.four;  /// 07: continued
   var x = topLevelFunction.bla;  /// 09: continued
   var x = C.bla;  /// 10: continued
   var x = zzTop.Frank;  /// 11: continued
 
   var x = new Rainbow();  /// 20: continued
   var x = new Rainbow();  /// 21: continued
   var x = new Rainbow();  /// 22: continued
 
   // It is a compile-time error to explicitly instantiate an enum instance.
   var x = new Color();  /// 30: compile-time error
 }