Use patching for dart:io.

lib/io/timer_impl.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.
 
 class _Timer implements Timer {
   // Set jitter to wake up timer events that would happen in _TIMER_JITTER ms.
   static const int _TIMER_JITTER = 0;
 
   // Disables the timer.
   static const int _NO_TIMER = -1;
@@ skipping 180 matching lines @@
 _getTimerFactoryClosure() {
   return (int milliSeconds, void callback(Timer timer), bool repeating) {
     if (repeating) {
       return new _Timer.repeating(milliSeconds, callback);
     }
     return new _Timer(milliSeconds, callback);
   };
 }