Submit handler to enable a disabled display.
public function submitDisplayEnable($form, &$form_state) {
$view = $this->entity;
$id = $form_state['display_id'];
// setOption doesn't work because this would might affect upper displays
$view
->get('executable')->displayHandlers
->get($id)
->setOption('enabled', TRUE);
// Store in cache
$view
->cacheSet();
// Redirect to the top-level edit page.
$form_state['redirect'] = 'admin/structure/views/view/' . $view
->id() . '/edit/' . $id;
}