Reapply setTimeout change.

tests/html/async_window_test.dart

 library AsyncWindowTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
+import 'dart:async';
 
 main() {
   useHtmlConfiguration();
-  test('Window.setTimeout', () {
-    window.setTimeout(expectAsync0((){}), 10);
+  test('Timer', () {
+    new Timer(const Duration(milliseconds: 10), expectAsync0((){}));
   });
-  test('Window.setInterval', () {
+  test('Timer.repeating', () {
     int counter = 0;
     int id = null;
-    id = window.setInterval(expectAsyncUntil0(
-      () {
-        if (counter == 3) {
-          counter = 1024;
-          window.clearInterval(id);
-          // Wait some more time to be sure callback won't be invoked any more.
-          window.setTimeout(expectAsync0((){}), 50);
-          return;
-        }
-        // As callback should have been cleared on 4th invocation, counter
-        // should never be greater than 3.
-        assert(counter < 3);
-        counter++;
-      },
-      () => counter == 3), 10);
+    new Timer.repeating(const Duration(milliseconds: 10),
+        expectAsyncUntil1(
+        (timer) {
+          if (counter == 3) {
+            counter = 1024;
+            timer.cancel();
+            // Wait some more time to be sure callback won't be invoked any
+            // more.
+            new Timer(const Duration(milliseconds: 50), expectAsync0((){}));
+            return;
+          }
+          // As callback should have been cleared on 4th invocation, counter
+          // should never be greater than 3.
+          assert(counter < 3);
+          counter++;
+        },
+        () => counter == 3));
   });
 }