Provide the default form for setting options.
Overrides PluginBase::buildOptionsForm
public function buildOptionsForm(&$form, &$form_state) {
parent::buildOptionsForm($form, $form_state);
$pager_text = $this->displayHandler
->getPagerText();
$form['items_per_page'] = array(
'#title' => $pager_text['items per page title'],
'#type' => 'textfield',
'#description' => $pager_text['items per page description'],
'#default_value' => $this->options['items_per_page'],
);
$form['offset'] = array(
'#type' => 'textfield',
'#title' => t('Offset (number of items to skip)'),
'#description' => t('For example, set this to 3 and the first 3 items will not be displayed.'),
'#default_value' => $this->options['offset'],
);
}