anchor.diff:  final _singletonParent = new ParentInteractiveHtmlConfiguration();
   final _singletonChild = new ChildInteractiveHtmlConfiguration();
   
  -String _CSS = """
  +const String _CSS = """
   body {
   font-family: Arial, sans-serif;
   margin: 0;
  
positive.code:     DateTime end = new DateTime.now();
      int elapsed = end.difference(_testStarts[testCase.id]).inMilliseconds;
      if (testCase.stackTrace != null) {
        parentWindow.postMessage(
            _Message.text(_Message.STACK, elapsed, testCase.stackTrace), '*');
      }
      parentWindow.postMessage(
          _Message.text(testCase.result, elapsed, testCase.message), '*');
    }
    void onSummary(int passed, int failed, int errors, List<TestCase> results,
  
negative.code:   void _handleMessage(MessageEvent e) {
      // Get the result, do any logging, then do a pass/fail.
      var msg = new _Message.fromString(e.data);
  
      if(msg == null) {
        return;
      }
      if (msg.messageType == _Message.LOG) {
        logMessage(e.data);
      } else if (msg.messageType == _Message.STACK) {
  