Enqueue superclasses instead of supertypes.

tests/compiler/dart2js/message_kind_test.dart

 // Copyright (c) 2013, 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 'dart:async';
 import "package:async_helper/async_helper.dart";
 import 'package:compiler/src/diagnostics/messages.dart' show
     MessageKind,
     MessageTemplate;
 
 import 'message_kind_helper.dart';
 
 main(List<String> arguments) {
   List<MessageTemplate> examples = <MessageTemplate>[];
   for (MessageKind kind in MessageKind.values) {
     MessageTemplate template = MessageTemplate.TEMPLATES[kind];
     Expect.isNotNull(template, "No template for $kind.");
     Expect.equals(kind, template.kind,
         "Invalid MessageTemplate.kind for $kind, found ${template.kind}.");
 
     String name = '${kind.toString()}'.substring('MessageKind.'.length);
     if (!arguments.isEmpty && !arguments.contains(name)) continue;
     if (name == 'GENERIC' // Shouldn't be used.
         // We can't provoke a crash.
         || name == 'COMPILER_CRASHED'
         || name == 'PLEASE_REPORT_THE_CRASH'
         // We cannot provide examples for patch errors.
         || name.startsWith('PATCH_')
-        || name == 'LIBRARY_NOT_SUPPORTED') continue;
+        || name == 'LIBRARY_NOT_SUPPORTED'
+        // TODO(johnniwinther): Remove these when [Compiler.reportUnusedCode] is
+        // reenabled.
+        || name == 'UNUSED_METHOD'
+        || name == 'UNUSED_CLASS'
+        || name == 'UNUSED_TYPEDEF') continue;
     if (template.examples != null) {
       examples.add(template);
     } else {
       print("No example in '$name'");
     }
   };
   var cachedCompiler;
   asyncTest(() => Future.forEach(examples, (MessageTemplate template) {
     print("Checking '${template.kind}'.");
     Stopwatch sw = new Stopwatch()..start();
     return check(template, cachedCompiler).then((var compiler) {
       cachedCompiler = compiler;
       sw.stop();
       print("Checked '${template.kind}' in ${sw.elapsedMilliseconds}ms.");
     });
   }));
 }