pkg/unittest: much cleaner support for arbitrary args in expectAsync functions

pkg/unittest/test/unittest_async_exception_test.dart

Index: pkg/unittest/test/unittest_async_exception_test.dart
diff --git a/pkg/unittest/test/unittest_async_exception_test.dart b/pkg/unittest/test/unittest_async_exception_test.dart
index 34298b7d275502227fa80a1d3a0ce6c024e465d3..cc351169debb8aee01d16c735e75e39e843541ba 100644
--- a/pkg/unittest/test/unittest_async_exception_test.dart
+++ b/pkg/unittest/test/unittest_async_exception_test.dart
@@ -13,8 +13,8 @@ var testName = 'async exception test';
 
 var testFunction = (_) {
   test(testName, () {
-    expectAsync0(() {});
-    _defer(() => guardAsync(() { throw "error!"; }));
+    expectAsync(() {});
+    _defer(() { throw "error!"; });
   });
 };