Only use special method to send messages to helper isolate.

tools/dom/src/Timer.dart

 // Copyright (c) 2012, 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.
 
 part of html;
 
-// TODO(antonm): support not DOM isolates too.
 class _Timer implements Timer {
   final canceller;
 
   _Timer(this.canceller);
 
   void cancel() { canceller(); }
 }
 
 get _timerFactoryClosure => (int milliSeconds, void callback(Timer timer), bool repeating) {
   var maker;
@@ skipping 30 matching lines @@
 
   void cancel() {
     _cancel();
     _send([_CANCEL_TIMER]);
   }
 
   void _cancel() {
     _port.close();
   }
 
-  // Tricky part.
-  // Once _HELPER_ISOLATE_PORT gets resolved, it will still delay in .then
-  // and to delay Timer.run is used. However, Timer.run will try to register
-  // another Timer and here we got stuck: event cannot be posted as then
-  // callback is not executed because it's delayed with timer.
-  // Therefore once future is resolved, it's unsafe to call .then on it
-  // in Timer code.
   _send(msg) {
-    if (_SEND_PORT != null) {
-      _SEND_PORT.send(msg, _sendPort);
-    } else {
-      _HELPER_ISOLATE_PORT.then((port) {
-        _SEND_PORT = port;
-        _SEND_PORT.send(msg, _sendPort);
-      });
-    }
+    _sendToHelperIsolate(msg, _sendPort);
   }
 }
 
 get _pureIsolateTimerFactoryClosure =>
     ((int milliSeconds, void callback(Timer time), bool repeating) =>
         new _PureIsolateTimer(milliSeconds, callback, repeating));