Give test more time.

tests/lib/async/timer_isActive_test.dart

 // Copyright (c) 2011, 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:unittest/unittest.dart';
 
 main() {
 
   test("timer isActive test", () {
@@ skipping 16 matching lines @@
       }
       i++;
     }
 
     t = new Timer.periodic(new Duration(milliseconds: 1),
                            expectAsync(checkActive, count: 3));
     expect(t.isActive, equals(true));
   });
 
   test("timer cancel test", () {
-    Timer timer = new Timer(const Duration(seconds: 1),
+    Timer timer = new Timer(const Duration(seconds: 15),
                             () => fail("Should not be reached."));
     Timer.run(expectAsync(() {
       expect(timer.isActive, equals(true));
       timer.cancel();
       expect(timer.isActive, equals(false));
     }));
   });
 }