Support enums in dart2dart.

tests/language/enum_private_lib.dart

Index: tests/language/enum_private_lib.dart
diff --git a/tests/html/deferred_multi_app_lib.dart b/tests/language/enum_private_lib.dart
similarity index 81%
copy from tests/html/deferred_multi_app_lib.dart
copy to tests/language/enum_private_lib.dart
index 6ec352d4a43cf336d85abaf9ebc816150ef0d007..c8fb00f6f3f757100cf1daa96a61ead3f92c0f8c 100644
--- a/tests/html/deferred_multi_app_lib.dart
+++ b/tests/language/enum_private_lib.dart
@@ -2,10 +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.
 
-one() {
-  return "one";
-}
+library enum_private_lib;
 
-two() {
-  return "two";
-}
+enum Enum2 {
+  _A,
+  _B,
+}