Fix typo in _DoneStreamSubscription.asFuture.

tests/lib/async/stream_controller_test.dart

 // Copyright (c) 2011, 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.
 
 // Test the basic StreamController and StreamController.singleSubscription.
 library stream_controller_test;
 
 import "package:expect/expect.dart";
 import "package:async_helper/async_helper.dart";
 import 'dart:async';
@@ skipping 591 matching lines @@
   StreamController c = new StreamController.broadcast();
   var f = c.close();
   f.then((_) {
     // Listening after close is allowed. The listener gets a done event.
     var sub = c.stream.listen(null, onDone: () {
       Expect.fail("wrong done");
     });
     sub.pause();
     sub.pause();
     new Timer(MS * 100, () {
+      sub.asFuture().whenComplete(() { Expect.fail("Bad complete"); });
       sub.resume();
       new Timer(MS * 100, () {
         sub.onDone(asyncEnd);
         sub.resume();
       });
     });
   });
 }
 
 void testAsBroadcastListenAfterClose() {
@@ skipping 17 matching lines @@
   s.listen(null, onDone: asyncEnd);
   var f = c.close();
   f.then((_) {
     // Listening after close is allowed. The listener gets a done event.
     var sub = s.listen(null, onDone: () {
       Expect.fail("wrong done");
     });
     sub.pause();
     sub.pause();
     new Timer(MS * 100, () {
+      sub.asFuture().whenComplete(() { Expect.fail("Bad complete"); });
       sub.resume();
       new Timer(MS * 100, () {
         sub.onDone(asyncEnd);
         sub.resume();
       });
     });
   });
 }
 
 main() {
   asyncStart();
   testMultiController();
   testSingleController();
   testExtraMethods();
   testClosed();
   testCloseFuture();
   testCloseFuture2();
   testCloseFuture3();
   testStreamEquals();
   testCancelThrow();
   testCancelThrow2();
   testCancelThrow3();
   testBroadcastListenAfterClose();
   testBroadcastListenAfterClosePaused();
   testAsBroadcastListenAfterClose();
   testAsBroadcastListenAfterClosePaused();
   asyncEnd();
 }