Revert "Dartium JS Interop enabled."

tests/html/worker_test.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 worker_test;
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_individual_config.dart';
 import 'dart:html';
 
 main() {
@@ skipping 32 matching lines @@
       var blob = new Blob([workerScript], 'text/javascript');
       var url = Url.createObjectUrl(blob);
       var worker = new Worker(url);
       var test = expectAsync((e) {
         expect(e.data, 'WorkerMessage');
       });
       worker.onMessage.first.then(test);
     });
   });
 }
+