Revert r20668.

sdk/lib/html/dart2js/html_dart2js.dart

Index: sdk/lib/html/dart2js/html_dart2js.dart
===================================================================
--- sdk/lib/html/dart2js/html_dart2js.dart	(revision 20693)
+++ sdk/lib/html/dart2js/html_dart2js.dart	(working copy)
@@ -32781,6 +32781,10 @@
   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.
@@ -32808,8 +32812,29 @@
   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));