Add test of unittests.

tests/compiler/dart2js/subtypeset_test.dart

 // Copyright (c) 2015, 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.
 
 // Test for iterators on for [SubclassNode].
 
-library world_test;
+library subtypeset_test;
 
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'type_test_helper.dart';
 import 'package:compiler/src/elements/elements.dart'
        show Element, ClassElement;
 import 'package:compiler/src/universe/class_set.dart';
 import 'package:compiler/src/world.dart';
 
 void main() {
@@ skipping 54 matching lines @@
     checkClass(B, [B, D, E]);
     checkClass(C, [C, E, F, G, H, B, D, I]);
     checkClass(D, [D]);
     checkClass(E, [E]);
     checkClass(F, [F]);
     checkClass(G, [G]);
     checkClass(H, [H, I]);
     checkClass(I, [I]);
   }));
 }