Enable enums by default.

pkg/compiler/lib/src/resolution/members.dart

 // Copyright (c) 2012, 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 resolution;
 
 abstract class TreeElements {
   AnalyzableElement get analyzedElement;
   Iterable<Node> get superUses;
 
@@ skipping 4250 matching lines @@
       if (superMember.isErroneous) {
         compiler.elementsWithCompileTimeErrors.add(constructor);
       }
       element.setDefaultConstructor(constructor, compiler);
     }
     return element.computeType(compiler);
   }
 
   @override
   DartType visitEnum(Enum node) {
-    if (!compiler.enableEnums) {
-      compiler.reportError(node, MessageKind.EXPERIMENTAL_ENUMS);
-    }
-
     if (element == null) {
       throw compiler.internalError(node, 'element is null');
     }
     if (element.resolutionState != STATE_STARTED) {
       throw compiler.internalError(element,
           'cyclic resolution of class $element');
     }
 
     InterfaceType enumType = element.computeType(compiler);
     element.supertype = compiler.objectClass.computeType(compiler);
@@ skipping 748 matching lines @@
 }
 
 /// The result for the resolution of the `assert` method.
 class AssertResult implements ResolutionResult {
   const AssertResult();
 
   Element get element => null;
 
   String toString() => 'AssertResult()';
 }