Sharing metatest logic between unittest and scheduled_test

pkg/scheduled_test/test/scheduled_test/unhandled_error_test.dart

 // Copyright (c) 2014, 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 'dart:async';
 
 import 'package:scheduled_test/scheduled_test.dart';
 
-import '../metatest.dart';
+import 'package:metatest/metatest.dart';
 import '../utils.dart';
 
-void main(_, message) {
+void main() => initTests(_test);
+
+void _test(message) {
   initMetatest(message);
 
   setUpTimeout();
 
   expectTestFails("a top-leveled error should be converted to a schedule error",
       () {
     schedule(() {
       new Future.microtask(() => throw 'error');
       return pumpEventQueue();
     });
   }, (errors) {
     expect(errors.first.error, equals('error'));
   });
 }