Make dart2js unittests async.

tests/compiler/dart2js/licm_test.dart

 // Copyright (c) 2013, 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.
 
 // Check that we hoist instructions in a loop condition, even if that
 // condition involves control flow.
 
-import 'package:expect/expect.dart';
-
+import 'package:async_helper/async_helper.dart';
 import 'compiler_helper.dart';
 
 const String TEST = '''
 var a = [1];
 
 main() {
   int count = int.parse('42') == 42 ? 42 : null;
   for (int i = 0; i < count && i < a[0]; i++) {
     print(i);
   }
   a.removeLast();
   // Ensure we don't try to generate a bailout method based on a check
   // of [count].
   count.removeLast();
 }
 ''';
 
 main() {
-  compileAndMatch(TEST, 'main',
-      new RegExp('if \\(typeof count !== "number"\\)(.|\\n)*while'));
+  asyncTest(() => compileAndMatch(TEST, 'main',
+      new RegExp('if \\(typeof count !== "number"\\)(.|\\n)*while')));
 }