WordPress at a glance
function is not described

wp_admin_bar_shortlink_menu() WP 3.1.0

Provide a shortlink.

No Hooks.

Return

Nothing (null).

Usage

wp_admin_bar_shortlink_menu( $wp_admin_bar );
$wp_admin_bar(WP_Admin_Bar) (required)

Code of wp admin bar shortlink menu: wp-includes/admin-bar.php VER 5.0.3

<?php
function wp_admin_bar_shortlink_menu( $wp_admin_bar ) {
	$short = wp_get_shortlink( 0, 'query' );
	$id = 'get-shortlink';

	if ( empty( $short ) )
		return;

	$html = '<input class="shortlink-input" type="text" readonly="readonly" value="' . esc_attr( $short ) . '" />';

	$wp_admin_bar->add_menu( array(
		'id' => $id,
		'title' => __( 'Shortlink' ),
		'href' => $short,
		'meta' => array( 'html' => $html ),
	) );
}