Support enums in dart2dart.

pkg/analyzer2dart/lib/src/modely.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.
 
 part of analyzer2dart.element_converter;
 
 
 /// Base [dart2js.Element] implementation for converted analyzer elements.
 class ElementY extends dart2js.Element {
   final ElementConverter converter;
@@ skipping 322 matching lines @@
   bool get isStatic {
     // Semantic difference: Analyzer considers top-level and static class
     // members to be static, dart2js only considers static class members to be
     // static.
     return false;
   }
 
   // TODO(johnniwinther): Ensure the correct semantics of this.
   @override
   bool get isAbstract => false;
+
+  @override
+  dart2js.ClassElement get enclosingClass => null;
 }
 
 abstract class FunctionElementMixin
     implements ElementY, dart2js.FunctionElement {
 
   // TODO(johnniwinther): Ensure the correct semantics of this.
   @override
   bool get isExternal => false;
 
   @override
@@ skipping 437 matching lines @@
 
   @override
   bool get isRedirectingFactory => unsupported('isRedirectingFactory');
 
   @override
   get nestedClosures => unsupported('nestedClosures');
 
   @override
   get type => unsupported('type');
 }