Update to Drupal 8.0.0-beta15. For more information, see: https://www.drupal.org/node/2563023

core/modules/contextual/js/views/VisualView.js

@@ -10,7 +10,10 @@
   Drupal.contextual.VisualView = Backbone.View.extend(/** @lends Drupal.contextual.VisualView# */{
 
     /**
+     * Events for the Backbone view.
+     *
      * @return {object}
+     *   A mapping of events to be used in the view.
      */
     events: function () {
       // Prevents delay and simulated mouse events.
@@ -46,6 +49,7 @@
      * @inheritdoc
      *
      * @return {Drupal.contextual.VisualView}
+     *   The current contextual visual view.
      */
     render: function () {
       var isOpen = this.model.get('isOpen');