Submit handler to add a restore a removed display to a view.
public function submitDisplayUndoDelete($form, &$form_state) {
$view = $this->entity;
// Create the new display
$id = $form_state['display_id'];
$displays = $view
->get('display');
$displays[$id]['deleted'] = FALSE;
$view
->set('display', $displays);
// Store in cache
$view
->cacheSet();
// Redirect to the top-level edit page.
$form_state['redirect'] = 'admin/structure/views/view/' . $view
->id() . '/edit/' . $id;
}