Add a test runner executable.

lib/src/invoker.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.
 
 library unittest.invoker;
 
 import 'dart:async';
 
 import 'package:stack_trace/stack_trace.dart';
 
@@ skipping 154 matching lines @@
         // If a [Future] returned from an error zone would throw an error
         // through the zone boundary, it instead never completes, and we want to
         // avoid that.
         _completer.future.then((_) {
           if (_test._tearDown == null) return null;
           return new Future.sync(_test._tearDown);
         }).catchError(Zone.current.handleUncaughtError).then((_) {
           timer.cancel();
           _controller.setState(
               new State(Status.complete, liveTest.state.result));
-          _controller.completer.complete();
+
+          // Use [Timer.run] here to avoid starving the DOM or other
+          // non-microtask events.
+          Timer.run(_controller.completer.complete);
         });
       }, zoneValues: {#unittest.invoker: this}, onError: handleError);
     });
   }
 }