Fix bug in VM timer implementation.

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 implements Timer {
   // Set jitter to wake up timer events that would happen in _TIMER_JITTER ms.
   static const int _TIMER_JITTER = 0;
 
@@ skipping 140 matching lines @@
           if (timer._callback != null) {
             timer._callback(timer);
             if (timer._repeating) {
               timer._advanceWakeupTime();
               timer._addTimerToList();
             }
           }
         }
       } finally {
         _handling_callbacks = false;
+        _notifyEventHandler();
       }
-      _notifyEventHandler();
     }
 
     if(_receivePort == null) {
       _receivePort = new ReceivePort();
       _receivePort.receive((var message, ignored) {
         _handleTimeout();
       });
     }
   }
 
@@ skipping 20 matching lines @@
 _getTimerFactoryClosure() {
   return (int milliSeconds, void callback(Timer timer), bool repeating) {
     if (repeating) {
       return new _Timer.periodic(milliSeconds, callback);
     }
     return new _Timer(milliSeconds, callback);
   };
 }