pkg/unittest: support up to 6 arguments in expectAsync[Until]

pkg/unittest/test/unittest_late_exception_test.dart

Index: pkg/unittest/test/unittest_late_exception_test.dart
diff --git a/pkg/unittest/test/unittest_late_exception_test.dart b/pkg/unittest/test/unittest_late_exception_test.dart
index 7a5c3e61cbdb86ddfad33eb31649c6ff00c1a6f2..c80de1263329dab9e81ad440aceee9b8036db5b5 100644
--- a/pkg/unittest/test/unittest_late_exception_test.dart
+++ b/pkg/unittest/test/unittest_late_exception_test.dart
@@ -14,11 +14,11 @@ var testName = 'late exception test';
 var testFunction = (_) {
   var f;
   test('testOne', () {
-    f = expectAsync0(() {});
+    f = expectAsync(() {});
     _defer(f);
   });
   test('testTwo', () {
-    _defer(expectAsync0(() { f(); }));
+    _defer(expectAsync(() { f(); }));
   });
 };