If a new timer is the last timer to time out, don't run through the entire list of timers.

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;
 
@@ skipping 61 matching lines @@
 
   void _advanceWakeupTime() {
     assert(_milliSeconds >= 0);
     _wakeupTime += _milliSeconds;
   }
 
   // Adds a timer to the timer list. Timers with the same wakeup time are
   // enqueued in order and notified in FIFO order.
   void _addTimerToList() {
     _Timer entry = _timers.isEmpty ? null : _timers.first;
+    // If timer is last, add to end.
+    if (entry == null || _timers.last._wakeupTime <= _wakeupTime) {
+      _timers.add(this);
+      return;
+    }
+    // Otherwise scan through and find the right position.
     while (entry != null) {
       if (_wakeupTime < entry._wakeupTime) {
         entry.insertBefore(this);
         return;
       }
       entry = entry.next;
     }
     _timers.add(this);
   }
 
@@ skipping 90 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);
   };
 }