Make the repeating argument to timers optional.

tests/standalone/src/TimerRepeatTest.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 TimerRepeatTest {
 
   static final int _TIMEOUT = 500;
   static final int _ITERATIONS = 5;
 
   static void testRepeatTimer() {
 
     void timeoutHandler(Timer timer) {
       int endTime = (new Date.now()).value;
       _iteration++;
       if (_iteration < _ITERATIONS) {
         _startTime = (new Date.now()).value;
       } else {
         Expect.equals(_iteration, _ITERATIONS);
         timer.cancel();
       }
     }
 
     _iteration = 0;
     _startTime = (new Date.now()).value;
-    timer = new Timer(timeoutHandler, _TIMEOUT, true);
+    timer = new Timer.repeating(timeoutHandler, _TIMEOUT);
   }
 
   static void testMain() {
     testRepeatTimer();
   }
 
   static Timer timer;
   static int _startTime;
   static int _iteration;
 }
 
 main() {
   TimerRepeatTest.testMain();
 }