diff -r 490d5cc509ed -r cf61fcea0001 wp/wp-includes/class-walker-category-dropdown.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/class-walker-category-dropdown.php	Mon Oct 14 17:39:30 2019 +0200
@@ -0,0 +1,77 @@
+<?php
+/**
+ * Taxonomy API: Walker_CategoryDropdown class
+ *
+ * @package WordPress
+ * @subpackage Template
+ * @since 4.4.0
+ */
+
+/**
+ * Core class used to create an HTML dropdown list of Categories.
+ *
+ * @since 2.1.0
+ *
+ * @see Walker
+ */
+class Walker_CategoryDropdown extends Walker {
+
+	/**
+	 * What the class handles.
+	 *
+	 * @since 2.1.0
+	 * @var string
+	 *
+	 * @see Walker::$tree_type
+	 */
+	public $tree_type = 'category';
+
+	/**
+	 * Database fields to use.
+	 *
+	 * @since 2.1.0
+	 * @todo Decouple this
+	 * @var array
+	 *
+	 * @see Walker::$db_fields
+	 */
+	public $db_fields = array ('parent' => 'parent', 'id' => 'term_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 object $category Category data object.
+	 * @param int    $depth    Depth of category. Used for padding.
+	 * @param array  $args     Uses 'selected', 'show_count', and 'value_field' keys, if they exist.
+	 *                         See wp_dropdown_categories().
+	 * @param int    $id       Optional. ID of the current category. Default 0 (unused).
+	 */
+	public function start_el( &$output, $category, $depth = 0, $args = array(), $id = 0 ) {
+		$pad = str_repeat('&nbsp;', $depth * 3);
+
+		/** This filter is documented in wp-includes/category-template.php */
+		$cat_name = apply_filters( 'list_cats', $category->name, $category );
+
+		if ( isset( $args['value_field'] ) && isset( $category->{$args['value_field']} ) ) {
+			$value_field = $args['value_field'];
+		} else {
+			$value_field = 'term_id';
+		}
+
+		$output .= "\t<option class=\"level-$depth\" value=\"" . esc_attr( $category->{$value_field} ) . "\"";
+
+		// Type-juggling causes false matches, so we force everything to a string.
+		if ( (string) $category->{$value_field} === (string) $args['selected'] )
+			$output .= ' selected="selected"';
+		$output .= '>';
+		$output .= $pad.$cat_name;
+		if ( $args['show_count'] )
+			$output .= '&nbsp;&nbsp;('. number_format_i18n( $category->count ) .')';
+		$output .= "</option>\n";
+	}
+}