Add 'self_check' runtime for running self-checking unit tests

pkg/kernel/test/class_hierarchy_test_disabled.dart

 // Copyright (c) 2016, 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:kernel/kernel.dart';
 import 'package:test/test.dart';
-import 'class_hierarchy_tester.dart';
+import 'class_hierarchy_self_check.dart';
 
 main() {
   test('All-pairs class hierarchy tests on dart2js', () {
     testClassHierarchyOnProgram(
         loadProgramFromBinary('test/data/dart2js.dill'));
   });
 }