diff -r 490d5cc509ed -r cf61fcea0001 wp/wp-includes/class-walker-page-dropdown.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/class-walker-page-dropdown.php	Mon Oct 14 17:39:30 2019 +0200
@@ -0,0 +1,87 @@
+<?php
+/**
+ * Post API: Walker_PageDropdown class
+ *
+ * @package WordPress
+ * @subpackage Post
+ * @since 4.4.0
+ */
+
+/**
+ * Core class used to create an HTML drop-down list of pages.
+ *
+ * @since 2.1.0
+ *
+ * @see Walker
+ */
+class Walker_PageDropdown extends Walker {
+
+	/**
+	 * What the class handles.
+	 *
+	 * @since 2.1.0
+	 * @var string
+	 *
+	 * @see Walker::$tree_type
+	 */
+	public $tree_type = 'page';
+
+	/**
+	 * Database fields to use.
+	 *
+	 * @since 2.1.0
+	 * @var array
+	 *
+	 * @see Walker::$db_fields
+	 * @todo Decouple this
+	 */
+	public $db_fields = array( 'parent' => 'post_parent', 'id' => 'ID' );
+
+	/**
+	 * Starts the element output.
+	 *
+	 * @since 2.1.0
+	 *
+	 * @see Walker::start_el()
+	 *
+	 * @param string  $output Used to append additional content. Passed by reference.
+	 * @param WP_Post $page   Page data object.
+	 * @param int     $depth  Optional. Depth of page in reference to parent pages. Used for padding.
+	 *                        Default 0.
+	 * @param array   $args   Optional. Uses 'selected' argument for selected page to set selected HTML
+	 *                        attribute for option element. Uses 'value_field' argument to fill "value"
+	 *                        attribute. See wp_dropdown_pages(). Default empty array.
+	 * @param int     $id     Optional. ID of the current page. Default 0 (unused).
+	 */
+	public function start_el( &$output, $page, $depth = 0, $args = array(), $id = 0 ) {
+		$pad = str_repeat('&nbsp;', $depth * 3);
+
+		if ( ! isset( $args['value_field'] ) || ! isset( $page->{$args['value_field']} ) ) {
+			$args['value_field'] = 'ID';
+		}
+
+		$output .= "\t<option class=\"level-$depth\" value=\"" . esc_attr( $page->{$args['value_field']} ) . "\"";
+		if ( $page->ID == $args['selected'] )
+			$output .= ' selected="selected"';
+		$output .= '>';
+
+		$title = $page->post_title;
+		if ( '' === $title ) {
+			/* translators: %d: ID of a post */
+			$title = sprintf( __( '#%d (no title)' ), $page->ID );
+		}
+
+		/**
+		 * Filters the page title when creating an HTML drop-down list of pages.
+		 *
+		 * @since 3.1.0
+		 *
+		 * @param string $title Page title.
+		 * @param object $page  Page data object.
+		 */
+		$title = apply_filters( 'list_pages', $title, $page );
+
+		$output .= $pad . esc_html( $title );
+		$output .= "</option>\n";
+	}
+}