Add code to the worker to fool isolate_helper into thinking it isn't the result of spawning an isol…

dart/site/try/bugs/isolate_worker_bug.dart

+// Copyright (c) 2014, 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.
+
+// Successful test: output div contains "future!".
+
+import 'dart:async';
+
+const greeting = "Hello, cool people doing nice things!";
+
+// Prints a greeting.
+void main() {
+  print(greeting);
+
+  new Future(() => print("future!"));
+}