Fix test to work on js-shell by avoiding a periodic timer.

tests/language/await_for_cancel_test.dart

 // Copyright (c) 2014, 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.
 
 import "dart:async";
 import "package:expect/expect.dart";
 import "package:async_helper/async_helper.dart";
 
-bool cancelled;
+bool canceled;
 
 test1() async {
-  cancelled = false;
+  canceled = false;
   try {
     StreamController controller = infiniteStreamController();
     outer: while(true) {
       await for (var x in controller.stream) {
         for (int j = 0; j < 10; j++) {
           if (j == 5) break outer;
         }
       }
     }
   } finally {
-    Expect.isTrue(cancelled);
+    Expect.isTrue(canceled);
   }
 }
 
 test2() async {
-  cancelled = false;
+  canceled = false;
   try {
     StreamController controller = infiniteStreamController();
     bool first = true;
     outer: while(true) {
       if (first) {
         first = false;
       } else {
         break;
       }
       await for (var x in controller.stream) {
         for (int j = 0; j < 10; j++) {
           if (j == 5) continue outer;
         }
       }
     }
   } finally {
-    Expect.isTrue(cancelled);
+    Expect.isTrue(canceled);
   }
 }
 
 test() async {
   await test1();
   await test2();
 }
 
 main() {
   asyncStart();
   test().then((_) {
     asyncEnd();
   });
 }
 
 
 // Create a stream that produces numbers [1, 2, ... ]
 StreamController infiniteStreamController() {
   StreamController controller;
   Timer timer;
   int counter = 0;
 
-  void tick(_) {
+  void tick() {
+    if (controller.isPaused) {
+      return;
+    }
+    if (canceled) {
+      return;
+    }
     counter++;
     controller.add(counter); // Ask stream to send counter values as event.
+    Timer.run(tick);
   }
 
   void startTimer() {
-    timer = new Timer.periodic(const Duration(milliseconds: 10), tick);
-  }
-
-  void stopTimer() {
-    if (timer != null) {
-      timer.cancel();
-      timer = null;
-    }
+    Timer.run(tick);
   }
 
   controller = new StreamController(
       onListen: startTimer,
-      onPause: stopTimer,
       onResume: startTimer,
       onCancel: () {
-        cancelled = true;
-        stopTimer();
+        canceled = true;
       });
 
   return controller;
 }