Support parsing of enums in dart2js.

tests/compiler/dart2js/unparser2_test.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.
 
 import "package:expect/expect.dart";
 import "package:compiler/implementation/scanner/scannerlib.dart";
 import "package:compiler/implementation/tree/tree.dart";
 
 import "package:compiler/implementation/dart2jslib.dart"
     show DiagnosticListener,
          Script;
 
 import "package:compiler/implementation/elements/elements.dart"
     show CompilationUnitElement,
          LibraryElement;
 
 import "package:compiler/implementation/elements/modelx.dart"
     show CompilationUnitElementX,
          LibraryElementX;
 
 main() {
   testClassDef();
   testClass1Field();
   testClass2Fields();
   testClass1Field1Method();
   testClass1Field2Method();
   testClassDefTypeParam();
+  testEnumDef();
+  testEnum1Value();
+  testEnum2Value();
+  testEnum3Value();
+  testEnum3CommaValue();
 }
 
 testClassDef() {
   compareCode('class T{}');
 }
 
 testClass1Field() {
   compareCode('class T{var x;}');
 }
 
 testClass2Fields() {
   compareCode('class T{var x;var y;}');
 }
 
 testClass1Field1Method() {
   compareCode('class T{var x;m(){}}');
 }
 
 testClass1Field2Method() {
   compareCode('class T{a(){}b(){}}');
 }
 
 testClassDefTypeParam() {
   compareCode('class T<X>{}');
 }
 
-void compareCode(String code) {
-  Expect.equals(code, doUnparse(code));
+testEnumDef() {
+  compareCode('enum T {}');
 }
 
+testEnum1Value() {
+  compareCode('enum T {A}');
+}
+
+testEnum2Value() {
+  compareCode('enum T {A,B}');
+}
+
+testEnum3Value() {
+  compareCode('enum T {A,B,C}');
+}
+
+testEnum3CommaValue() {
+  compareCode('enum T {A,B,C,}', expectedResult: 'enum T {A,B,C}');
+}
+
+void compareCode(String code, {String expectedResult}) {
+  if (expectedResult == null) {
+    expectedResult = code;
+  }
+  Expect.equals(expectedResult, doUnparse(code));
+}
+
+
 String doUnparse(String source) {
   MessageCollector diagnosticListener = new MessageCollector();
   Script script = new Script(null, null, null);
   LibraryElement lib = new LibraryElementX(script);
   CompilationUnitElement element = new CompilationUnitElementX(script, lib);
   StringScanner scanner = new StringScanner.fromString(source);
   Token beginToken = scanner.tokenize();
   NodeListener listener = new NodeListener(diagnosticListener, element);
   Parser parser = new Parser(listener);
   parser.parseUnit(beginToken);
@@ skipping 11 matching lines @@
     messages.add(reason);
     throw reason;
   }
 
   void log(message) {
     messages.add(message);
   }
 
   noSuchMethod(Invocation invocation) => throw 'unsupported operation';
 }