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

test/runner/load_suite_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.
 
 @TestOn("vm")
 
 import 'dart:async';
 
 import 'package:test/src/backend/group.dart';
 import 'package:test/src/backend/state.dart';
@@ skipping 128 matching lines @@
 
       var liveTest = await (suite.group.entries.single as Test).load(suite);
       await liveTest.run();
       expectTestPassed(liveTest);
     });
 
     test("doesn't run change() if the suite is null", () async {
       var suite = new LoadSuite("name", SuiteConfiguration.empty, () => null);
       expect(suite.group.entries, hasLength(1));
 
-      var newSuite = suite.changeSuite(expectAsync((_) {}, count: 0));
+      var newSuite = suite.changeSuite(expectAsync1((_) {}, count: 0));
       expect(newSuite.suite, completion(isNull));
 
       var liveTest = await (suite.group.entries.single as Test).load(suite);
       await liveTest.run();
       expectTestPassed(liveTest);
     });
   });
 
   group("getSuite()", () {
     test("runs the test and returns the suite", () {
       var suite = new LoadSuite.forSuite(innerSuite);
       expect(suite.group.entries, hasLength(1));
 
       expect(suite.getSuite(), completion(equals(innerSuite)));
     });
 
     test("forwards errors to the future", () {
       var suite = new LoadSuite("name", SuiteConfiguration.empty,
           () => throw "error");
       expect(suite.group.entries, hasLength(1));
 
       expect(suite.getSuite(), throwsA("error"));
     });
   });
 }