Provide a list of core's block caching modes.
protected function blockCachingModes() {
return array(
DRUPAL_NO_CACHE => t('Do not cache'),
DRUPAL_CACHE_GLOBAL => t('Cache once for everything (global)'),
DRUPAL_CACHE_PER_PAGE => t('Per page'),
DRUPAL_CACHE_PER_ROLE => t('Per role'),
DRUPAL_CACHE_PER_ROLE | DRUPAL_CACHE_PER_PAGE => t('Per role per page'),
DRUPAL_CACHE_PER_USER => t('Per user'),
DRUPAL_CACHE_PER_USER | DRUPAL_CACHE_PER_PAGE => t('Per user per page'),
);
}