Make enum a keyword in dart2js.

tests/language/enum_is_keyword_test.dart

Index: tests/language/enum_is_keyword_test.dart
diff --git a/tests/compiler/dart2js/dart2js_batch2_run.dart b/tests/language/enum_is_keyword_test.dart
similarity index 62%
copy from tests/compiler/dart2js/dart2js_batch2_run.dart
copy to tests/language/enum_is_keyword_test.dart
index aee55ef18e5fa77c47bcbf53f5c16125299ed77a..2d24d94810ab6c41b7cc44c42d7a98d5116df763 100644
--- a/tests/compiler/dart2js/dart2js_batch2_run.dart
+++ b/tests/language/enum_is_keyword_test.dart
@@ -2,9 +2,9 @@
 // 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.
 
-@notExisting
-var x;
+// Test that `enum` is considered a keyword and therefore invalid as the name of
+// declarations.
 
 main() {
-  print(x);
+  var enum; /// 01: compile-time error
 }