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

dart/site/try/leap.dart

 // Copyright (c) 2013, 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.
 
 library trydart.main;
 
 import 'dart:async';
 import 'dart:html';
 import 'dart:isolate';
 
@@ skipping 397 matching lines @@
   onDone(_) {
     isDone = true;
     receivePort.close();
   }
 
   // This is called in browsers that support creating Object URLs in a
   // web worker.  For example, Chrome and Firefox 21.
   onUrl(String url) {
     objectUrls.add(url);
     clear();
-    String wrapper =
-        'function dartPrint(msg) { self.postMessage(msg); };'
-        'self.importScripts("$url");';
+    String wrapper = '''
+// Fool isolate_helper.dart so it does not think this is an isolate.
+var window = self;
+function dartPrint(msg) {
+  self.postMessage(msg);
+};
+self.importScripts("$url");
+''';
     var wrapperUrl =
         Url.createObjectUrl(new Blob([wrapper], 'application/javascript'));
     objectUrls.add(wrapperUrl);
     void retryInIframe(_) {
       var frame = makeOutputFrame(url);
       outputFrame.replaceWith(frame);
       outputFrame = frame;
     }
     void onError(String errorMessage) {
       console.appendText(errorMessage);
@@ skipping 886 matching lines @@
 }
 
 .center {
   display: block;
   margin: 0px auto;
   text-align: center;
 }
 """;
 
 ''';