Sharing metatest logic between unittest and scheduled_test

pkg/unittest/test/breath_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.
 
 library unittest.breath_test;
 
 import 'dart:async';
 
 import 'package:unittest/unittest.dart';
 
 void main() {
   // Test the sync test 'breath' feature of unittest.
 
   group('breath', () {
     var sentinel = 0;
     var start;
 
     test('initial', () {
-      Timer.run(() { sentinel = 1; });
+      Timer.run(() {
+        sentinel = 1;
+      });
     });
 
     test('starve', () {
       start = new DateTime.now().millisecondsSinceEpoch;
       var now;
       do {
         expect(sentinel, 0);
         now = new DateTime.now().millisecondsSinceEpoch;
       } while (now - start <= BREATH_INTERVAL);
     });
 
     test('breathed', () {
       expect(sentinel, 1);
     });
   });
 }