Add isActive field on Timer.

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 32 matching lines @@
   _Timer._internal() {}
 
   void _clear() {
     _callback = null;
     _milliSeconds = 0;
     _wakeupTime = 0;
   }
 
   bool get _repeating => _milliSeconds >= 0;
 
+  bool get _isActive => _timers.contains(this);

[floitsch, 2013/07/01 12:49:43]

contains is a linear operation.
Reuse _callback instead.
It is currently not cleared for single-shot timers, but that's easy to add in
line 148.

[zarah, 2013/07/01 16:15:35]

Done.

+
 
   // Cancels a set timer. The timer is removed from the timer list and if
   // the given timer is the earliest timer the native timer is reset.
   void cancel() {
     _clear();
     // Return if already canceled.
     if (list == null) return;
     assert(!_timers.isEmpty);
     _Timer first = _timers.first;
     unlink();
@@ skipping 113 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);
   };
 }