Support enums in dart2dart.

tests/language/language_dart2js.status

 # 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.
 
 [ $compiler == dart2js && $csp && $browser ]
 deferred_mixin_test: RuntimeError # Issue 21863
 
 [ $compiler == dart2js ]
 async_control_structures_test: CompileTimeError # Issue 21411
 async_test/none: CompileTimeError # Issue 21411
@@ skipping 190 matching lines @@
 [ $compiler == dart2dart && $builder_tag == new_backend && $minified == false ]
 # This test happens not to fail in minified, because the type-argument is
 # renamed, but the unresolved reference to it is not.
 type_variable_conflict2_test/04: Fail # Issue 19725
 
 [ $compiler == dart2dart && $minified && $builder_tag != new_backend ]
 type_variable_conflict2_test/01: RuntimeError # Issue 16180
 
 [ $compiler == dart2dart ]
 regress_13494_test: Fail # Issue 13494
-enum_const_test/01: Crash # Issue 21681
-enum_const_test/02: Crash # Issue 21681
 
+enum_duplicate_test/01: CompileTimeError # Issue 22169
 
 built_in_identifier_prefix_test: Fail # Issue 6972
 constructor_initializer_test/none: Fail # Issue 12633
 
 # Mixins fail on the VM.
 mixin_with_two_implicit_constructors_test: Fail # Issue 11889
 
 # Calling unresolved class constructor:
 call_nonexistent_constructor_test/01: Fail # Issue 13082
 call_nonexistent_constructor_test/02: Fail # Issue 13082
@@ skipping 47 matching lines @@
 invocation_mirror_test: Fail, OK # Issue 12706 (hardcoded names).
 super_call4_test: Fail, OK # hardcoded names.
 
 [ $minified ]
 stack_trace_test: Fail, OK # Stack trace not preserved in minified code.
 regress_21795_test: RuntimeError # Issue 12605
 
 [ $compiler == dart2js && $runtime == d8 && $system == windows ]
 *deferred*: Skip # Issue 17458
 cha_deopt*: Skip # Issue 17458