Very simple version of Isolates.

sdk/lib/io/timer_impl.dart

 // Copyright (c) 2013, 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 dart.io;
 
 class _Timer extends LinkedListEntry<_Timer> implements Timer {
   // Disables the timer.
   static const int _NO_TIMER = -1;
 
   // Timers are ordered by wakeup time.
   static LinkedList<_Timer> _timers = new LinkedList<_Timer>();
 
-  static ReceivePort _receivePort;
+  static RawReceivePort _receivePort;
+  static StreamSubscription _subscription;

[Ivan Posva, 2013/10/24 06:48:38]

Where is this _subscription used?

[floitsch, 2013/10/24 16:15:58]

spurious code from the ReceivePort -> RawReceivePort transition.
removed.

   static bool _handling_callbacks = false;
 
   Function _callback;
   int _milliSeconds;
   int _wakeupTime;
 
   static Timer _createTimer(void callback(Timer timer),
                             int milliSeconds,
                             bool repeating) {
     _Timer timer = new _Timer._internal();
@@ skipping 131 matching lines @@
             }
           }
         }
       } finally {
         _handling_callbacks = false;
         _notifyEventHandler();
       }
     }
 
     if(_receivePort == null) {
-      _receivePort = new ReceivePort();
-      _receivePort.receive((var message, ignored) {
-        _handleTimeout();
-      });
+      _receivePort = new RawReceivePort((message) { _handleTimeout(); });
     }
   }
 
   void _shutdownTimerHandler() {
     _receivePort.close();
     _receivePort = null;
   }
 }
 
 // Provide a closure which will allocate a Timer object to be able to hook
 // up the Timer interface in dart:isolate with the implementation here.
 _getTimerFactoryClosure() {
   return (int milliSeconds, void callback(Timer timer), bool repeating) {
     if (repeating) {
       return new _Timer.periodic(milliSeconds, callback);
     }
     return new _Timer(milliSeconds, callback);
   };
 }