Reapply "Reduce footprint of HTML Timer by not creating a "cancel" closure."

tools/dom/src/native_DOMImplementation.dart

Index: tools/dom/src/native_DOMImplementation.dart
diff --git a/tools/dom/src/native_DOMImplementation.dart b/tools/dom/src/native_DOMImplementation.dart
index d4ed796b16201c2d1f1134cdffc56c21ab9959f3..e54cc11752fab6f3ffdae5ef74a1b89207ac1e94 100644
--- a/tools/dom/src/native_DOMImplementation.dart
+++ b/tools/dom/src/native_DOMImplementation.dart
@@ -530,36 +530,33 @@ final _pureIsolateUriBaseClosure = () {
                                "is not supported in the browser");
 };
 
-class _Timer implements Timer {
-  const int _STATE_TIMEOUT = 0;
-  const int _STATE_INTERVAL = 1;
-  var _state;
+ class _Timer implements Timer {
+  var _canceler;
 
   _Timer(int milliSeconds, void callback(Timer timer), bool repeating) {
+
     if (repeating) {
-      _state = window._setInterval(() {
+      int id = window._setInterval(() {
         callback(this);
-      }, milliSeconds) * 2 + _STATE_INTERVAL;
+      }, milliSeconds);
+      _canceler = () => window._clearInterval(id);
     } else {
-      _state = window._setTimeout(() {
-        _state = null;
+      int id = window._setTimeout(() {
+        _canceler = null;
         callback(this);
-      }, milliSeconds) * 2 + _STATE_TIMEOUT;
+      }, milliSeconds);
+      _canceler = () => window._clearTimeout(id);
     }
   }
 
   void cancel() {
-    if (_state == null) return;
-    int id = _state ~/ 2;
-    if ((_state & 1) == _STATE_TIMEOUT) {
-      window._clearTimeout(id);
-    } else {
-      window._clearInterval(id);
+    if (_canceler != null) {
+      _canceler();
     }
-    _state = null;
+    _canceler = null;
   }
 
-  bool get isActive => _state != null;
+  bool get isActive => _canceler != null;
 }
 
 get _timerFactoryClosure =>