Use "self" not "window" for Worker API.

dart/tests/html/worker_api_test.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.
+
+import 'dart:html';
+import 'dart:isolate';
+
+import 'package:unittest/unittest.dart';
+import 'package:unittest/html_config.dart';
+
+worker() {
+  port.receive((String uri, SendPort replyTo) {
+    try {
+      var url = Url.createObjectUrl(new Blob([''], 'application/javascript'));
+      Url.revokeObjectUrl(url);
+      replyTo.send('Hello from Worker');
+    } catch (e) {
+      replyTo.send('Error: $e');
+    }
+    port.close();
+  });
+}
+
+main() {
+  useHtmlConfiguration();
+
+  test('stress test', () {
+    spawnFunction(worker).call('').then(
+        expectAsync1((reply) => expect(reply, equals('Hello from Worker'))));
+  });
+}