public function updateSearchableFields(&$fields) {

		// Instantiate a field containing the existing tags.

		$fields = array_merge(array(
			'Tagging' => array(
				'title' => 'Tags',
				'field' => ListboxField::create(
					'Tagging',
					'Tags',
					FusionTag::get()->map('Title', 'Title')->toArray(),
					(Controller::has_curr() && ($filtering = Controller::curr()->getRequest()->getVar('q')) && isset($filtering['Tagging'])) ? $filtering['Tagging'] : array(),
					null,
					true
				),
				'filter' => $this->owner->dbObject('Tagging')->stat('default_search_filter_class')
			)
		), $fields);

		// Allow extension.

		$this->owner->extend('updateTaggingExtensionSearchableFields', $fields);
	}