Revert r20668.

tools/dom/src/Timer.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.
 
 part of html;
 
 // TODO(antonm): support not DOM isolates too.
 class _Timer implements Timer {
   final canceller;
 
@@ skipping 11 matching lines @@
   } else {
     maker = window._setTimeout;
     canceller = window._clearTimeout;
   }
   Timer timer;
   final int id = maker(() { callback(timer); }, milliSeconds);
   timer = new _Timer(() { canceller(id); });
   return timer;
 };
 
+const _NEW_TIMER = 'NEW_TIMER';
+const _CANCEL_TIMER = 'CANCEL_TIMER';
+const _TIMER_PING = 'TIMER_PING';
+
 class _PureIsolateTimer implements Timer {
   final ReceivePort _port = new ReceivePort();
   SendPort _sendPort; // Effectively final.
 
   _PureIsolateTimer(int milliSeconds, callback, repeating) {
     _sendPort = _port.toSendPort();
     _port.receive((msg, replyTo) {
       assert(msg == _TIMER_PING);
       callback(this);
       if (!repeating) _cancel();
     });
     _HELPER_ISOLATE_PORT.then((port) {
       port.send([_NEW_TIMER, milliSeconds, repeating], _sendPort);
     });
   }
 
   void cancel() {
     _cancel();
     _HELPER_ISOLATE_PORT.then((port) {
       port.send([_CANCEL_TIMER], _sendPort);
     });
   }
 
   void _cancel() {
     _port.close();
   }
+
+  static final Future<SendPort> _HELPER_ISOLATE_PORT =
+      spawnDomFunction(_helperIsolateMain);
+}
+
+final _TIMER_REGISTRY = new Map<SendPort, Timer>();
+
+_helperIsolateMain() {
+  port.receive((msg, replyTo) {
+    final cmd = msg[0];
+    if (cmd == _NEW_TIMER) {
+      final duration = new Duration(milliseconds: msg[1]);
+      bool periodic = msg[2];
+      final callback = () { replyTo.send(_TIMER_PING); };
+      _TIMER_REGISTRY[replyTo] = periodic ?
+          new Timer.periodic(duration, callback) :
+          new Timer(duration, callback);
+    } else if (cmd == _CANCEL_TIMER) {
+      _TIMER_REGISTRY.remove(replyTo).cancel();
+    }
+  });
 }
 
 get _pureIsolateTimerFactoryClosure =>
     ((int milliSeconds, void callback(Timer time), bool repeating) =>
         new _PureIsolateTimer(milliSeconds, callback, repeating));