Adds “Add New” menu.

function wp_admin_bar_new_content_menu( $wp_admin_bar ) {
	$actions = array();

	$cpts = (array) get_post_types( array( 'show_in_admin_bar' => true ), 'objects' );

	if ( isset( $cpts['post'] ) && current_user_can( $cpts['post']->cap->create_posts ) ) {
		$actions['post-new.php'] = array( $cpts['post']->labels->name_admin_bar, 'new-post' );
	}

	if ( isset( $cpts['attachment'] ) && current_user_can( 'upload_files' ) ) {
		$actions['media-new.php'] = array( $cpts['attachment']->labels->name_admin_bar, 'new-media' );
	}

	if ( current_user_can( 'manage_links' ) ) {
		$actions['link-add.php'] = array( _x( 'Link', 'add new from admin bar' ), 'new-link' );
	}

	if ( isset( $cpts['page'] ) && current_user_can( $cpts['page']->cap->create_posts ) ) {
		$actions['post-new.php?post_type=page'] = array( $cpts['page']->labels->name_admin_bar, 'new-page' );
	}

	unset( $cpts['post'], $cpts['page'], $cpts['attachment'] );

	// Add any additional custom post types.
	foreach ( $cpts as $cpt ) {
		if ( ! current_user_can( $cpt->cap->create_posts ) ) {
			continue;
		}

		$key             = 'post-new.php?post_type=' . $cpt->name;
		$actions[ $key ] = array( $cpt->labels->name_admin_bar, 'new-' . $cpt->name );
	}
	// Avoid clash with parent node and a 'content' post type.
	if ( isset( $actions['post-new.php?post_type=content'] ) ) {
		$actions['post-new.php?post_type=content'][1] = 'add-new-content';
	}

	if ( current_user_can( 'create_users' ) || ( is_multisite() && current_user_can( 'promote_users' ) ) ) {
		$actions['user-new.php'] = array( _x( 'User', 'add new from admin bar' ), 'new-user' );
	}

	if ( ! $actions ) {
		return;
	}

	$title = '' . _x( 'New', 'admin bar menu group label' ) . '';

	$wp_admin_bar->add_node(
		array(
			'id'    => 'new-content',
			'title' => $title,
			'href'  => admin_url( current( array_keys( $actions ) ) ),
		)
	);

	foreach ( $actions as $link => $action ) {
		list( $title, $id ) = $action;

		$wp_admin_bar->add_node(
			array(
				'parent' => 'new-content',
				'id'     => $id,
				'title'  => $title,
				'href'   => admin_url( $link ),
			)
		);
	}
}