public void OnBeforeDocumentUnregister(object sender, DocumentRegisterationEventArgs eventArgs)
 {
     foreach (var subscriber in _subscriptionProvider.GetSubscribers<IWindowEventSubscriber> (eventArgs.DocumentHandle))
       {
     PrepareNavigation -= subscriber.OnPrepareNavigation;
     ViewCreated -= subscriber.OnViewCreated;
       }
 }
 private void OnDocumentRegistered (object sender, DocumentRegisterationEventArgs e)
 {
   HtmlDocument document;
   if (_currentDocuments != null && _currentDocuments.TryGetValue (e.DocumentHandle, out document))
     document.InvokeScript (c_registrationDoneCallback);
 }