Add expectAsyncX and expectAsyncUntilX methods, and deprecate the old methods.

test/frontend/tear_down_all_test.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.
 
 import 'dart:async';
 
 import 'package:async/async.dart';
 import 'package:test/test.dart';
 
 import '../utils.dart';
@@ skipping 244 matching lines @@
 
         test("after", () {
           expect(tearDownAllRun, isTrue);
         });
       });
     });
   });
 
   test("isn't run for a skipped group", () async {
     // Declare this in the outer test so if it runs, the outer test will fail.
-    var shouldNotRun = expectAsync(() {}, count: 0);
+    var shouldNotRun = expectAsync0(() {}, count: 0);
 
     var engine = declareEngine(() {
       group("skipped", () {
         tearDownAll(shouldNotRun);
 
         test("test", () {});
       }, skip: true);
     });
 
     await engine.run();
@@ skipping 56 matching lines @@
       expect(engine.liveTests, contains(tearDownAllLiveTest));
       expect(engine.failed, contains(tearDownAllLiveTest));
       expect(engine.passed, isNot(contains(tearDownAllLiveTest)));
       expect(engine.skipped, isNot(contains(tearDownAllLiveTest)));
       expect(engine.active, isNot(contains(tearDownAllLiveTest)));
     });
 
     test("runs further tearDownAlls", () async {
       // Declare this in the outer test so if it doesn't runs, the outer test
       // will fail.
-      var shouldRun = expectAsync(() {});
+      var shouldRun = expectAsync0(() {});
 
       var engine = declareEngine(() {
         tearDownAll(() => throw "error");
         tearDownAll(shouldRun);
 
         test("test", () {});
       });
 
       expect(await engine.run(), isFalse);
     });
 
     test("runs outer tearDownAlls", () async {
       // Declare this in the outer test so if it doesn't runs, the outer test
       // will fail.
-      var shouldRun = expectAsync(() {});
+      var shouldRun = expectAsync0(() {});
 
       var engine = declareEngine(() {
         tearDownAll(shouldRun);
 
         group("group", () {
           tearDownAll(() => throw "error");
 
           test("test", () {});
         });
       });
 
       expect(await engine.run(), isFalse);
     });
   });
 }