Fix flaky stream_controller_async_test.

tests/lib/async/stream_controller_async_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_async_test;
 
 import 'dart:async';
 import 'dart:isolate';
 import "package:expect/expect.dart";
@@ skipping 621 matching lines @@
     var done = expectAsync0((){});
     var c = broadcast ? new StreamController.broadcast(sync: sync)
                       : new StreamController(sync: sync);
     var expected = new Events()
         ..add(42)..error("error")
         ..add(1)..add(2)..add(3)
         ..add(4)..add(5)..add(43)..close();
     var stream = asBroadcast ? c.stream.asBroadcastStream() : c.stream;
     var actual = new Events();
     var sub;
     var pauseIsDone = false;

[floitsch, 2013/10/16 11:42:44]

variable can be removed now.

     sub = stream.listen(
         (v) {
           if (v == 3) {
             sub.pause(new Future.delayed(const Duration(milliseconds: 15),
                                          () { pauseIsDone = true; }));
           }
           actual.add(v);
         },
         onError: actual.error,
         onDone: actual.close);
     var sink = c.sink;
     sink.add(42);
     sink.addError("error");
     sink.addStream(new Stream.fromIterable([1, 2, 3, 4, 5]))
         .then((_) {
           sink.add(43);
           return sink.close();
         })
         .then((_) {
           if (asBroadcast || broadcast) {
             // The done-future of the sink completes when it passes
             // the done event to the asBroadcastStream controller, which is
             // before the final listener gets the event.
-            // Wait for the pause to end before testing the events.
-            dynamic executeWhenPauseIsDone(Function f) {
-              if (!pauseIsDone) {
-                return new Future.delayed(const Duration(milliseconds: 50), () {
-                  return executeWhenPauseIsDone(f);
-                });
-              }
-              return f();
-            }
-            return executeWhenPauseIsDone(() {
+            // Wait for the done event to be *delivered* before testing the
+            // events.
+            actual.onDone(() {
               Expect.listEquals(expected.events, actual.events);
               done();
             });
           } else {
             Expect.listEquals(expected.events, actual.events);
             done();
           }
         });
   });
 }
 
 main() {
   testController();
   testSingleController();
   testExtraMethods();
   testPause();
   testRethrow();
   testBroadcastController();
   testAsBroadcast();
   testSink(sync: true, broadcast: false, asBroadcast: false);
   testSink(sync: true, broadcast: false, asBroadcast: true);
   testSink(sync: true, broadcast: true, asBroadcast: false);
   testSink(sync: false, broadcast: false, asBroadcast: false);
   testSink(sync: false, broadcast: false, asBroadcast: true);
   testSink(sync: false, broadcast: true, asBroadcast: false);
 }