Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/path/path.js

@@ -0,0 +1,25 @@
+/**
+ * @file
+ * Attaches behaviors for the Path module.
+ */
+(function ($) {
+
+  "use strict";
+
+  /**
+   *
+   * @type {Drupal~behavior}
+   */
+  Drupal.behaviors.pathDetailsSummaries = {
+    attach: function (context) {
+      $(context).find('.path-form').drupalSetSummary(function (context) {
+        var path = $('.form-item-path-0-alias input').val();
+
+        return path ?
+          Drupal.t('Alias: @alias', {'@alias': path}) :
+          Drupal.t('No alias');
+      });
+    }
+  };
+
+})(jQuery);