Make the repeating argument to timers optional.

runtime/bin/timer_impl.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.
 
 class _Timer implements Timer {
 
   /*
    * Set jitter to wake up timer events that would happen in _TIMER_JITTER ms.
    */
   static final int _TIMER_JITTER = 0;
 
   /*
    * Disables the timer.
    */
   static final int _NO_TIMER = -1;
 
   factory _Timer(void callback(Timer timer),
                  int milliSeconds,
-                 bool repeating) {
+                 [bool repeating = false]) {
     EventHandler._start();
     if (_timers === null) {
       _timers = new DoubleLinkedQueue<_Timer>();
     }
     Timer timer = new _Timer._internal();
     timer._callback = callback;
     timer._milliSeconds = milliSeconds;
     timer._wakeupTime = (new Date.now()).value + milliSeconds;
     timer._repeating = repeating;
     timer._addTimerToList();
@@ skipping 147 matching lines @@
 
   static ReceivePort _receivePort;
   static bool _handling_callbacks = false;
 
   var _callback;
   int _milliSeconds;
   int _wakeupTime;
   bool _repeating;
 }