revert 1204. Will investigate when I get a chance.

pkg/unittest/html_config.dart

 // Copyright (c) 2011, 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.
 
 /**
  * A simple unit test library for running tests in a browser.
  */
 #library('unittest');
 
 #import('dart:html');
@@ skipping 27 matching lines @@
     window.on.error.remove(_onErrorClosure);
     _showResultsInPage(passed, failed, errors, results, _isLayoutTest,
         uncaughtError);
     window.postMessage('unittest-suite-done', '*');
   }
 }
 
 void useHtmlConfiguration([bool isLayoutTest = false]) {
   configure(new HtmlConfiguration(isLayoutTest));
 }