Files.app: prevent unlimited recursive directory traversal

chrome/browser/resources/file_manager/js/sidebar.js

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 'use strict';
 
 /**
  * Updates sub-elements of {@code parentElement} reading {@code DirectoryEntry}
  * with calling {@code iterator}.
  *
@@ skipping 146 matching lines @@
   eject.hidden = !PathUtil.isUnmountableByUser(path);
   eject.addEventListener('click',
       function(event) {
         event.stopPropagation();
         if (!PathUtil.isUnmountableByUser(path))
           return;
 
         volumeManager.unmount(path, function() {}, function() {});
       }.bind(this));
 
-  if ('expanded' in parentDirItem || parentDirItem.expanded)
+  if (parentDirItem.expanded)
     this.updateSubDirectories_();
 };
 
 /**
  * Invoked when the item is being expanded.
  * @param {!UIEvent} e Event.
  * @private
  **/
 DirectoryItem.prototype.onExpand_ = function(e) {
   this.updateSubDirectories_(function() {
@@ skipping 83 matching lines @@
  * @param {HTMLElement} el Element to be DirectoryTree.
  * @param {DirectoryModel} directoryModel Current DirectoryModel.
  */
 DirectoryTree.decorate = function(el, directoryModel) {
   el.__proto__ = DirectoryTree.prototype;
   (/** @type {DirectoryTree} */ el).decorate(directoryModel);
 };
 
 DirectoryTree.prototype = {
   __proto__: cr.ui.Tree.prototype,
+
+  // DirectoryTree is always expanded.
+  get expanded() { return true; },
+  /**
+   * @param {boolean} value Not used.
+   */
+  set expanded(value) {}
 };
 
 /**
  * Decorates an element.
  * @param {DirectoryModel} directoryModel Current DirectoryModel.
  */
 DirectoryTree.prototype.decorate = function(directoryModel) {
   cr.ui.Tree.prototype.decorate.call(this);
 
   this.directoryModel_ = directoryModel;
@@ skipping 50 matching lines @@
   this.setContextMenu(this.contextMenu_);
 };
 
 /**
  * Returns the path of the selected item.
  * @return {string} The current path.
  */
 DirectoryTree.prototype.getCurrentPath = function() {
   return this.selectedItem ? this.selectedItem.fullPath : null;
 };