Files.app: prevent unlimited recursive directory traversal

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

Index: chrome/browser/resources/file_manager/js/sidebar.js
diff --git a/chrome/browser/resources/file_manager/js/sidebar.js b/chrome/browser/resources/file_manager/js/sidebar.js
index f6d87448e38d0083b117abd58daf250d5cfd2b80..8ebc29342de17e3e8475647488485d9c21855801 100644
--- a/chrome/browser/resources/file_manager/js/sidebar.js
+++ b/chrome/browser/resources/file_manager/js/sidebar.js
@@ -164,7 +164,7 @@ DirectoryItem.prototype.decorate = function(
         volumeManager.unmount(path, function() {}, function() {});
       }.bind(this));
 
-  if ('expanded' in parentDirItem || parentDirItem.expanded)
+  if (parentDirItem.expanded)
     this.updateSubDirectories_();
 };
 
@@ -268,6 +268,13 @@ DirectoryTree.decorate = function(el, directoryModel) {
 
 DirectoryTree.prototype = {
   __proto__: cr.ui.Tree.prototype,
+
+  // DirectoryTree is always expanded.
+  get expanded() { return true; },
+  /**
+   * @param {boolean} value Not used.
+   */
+  set expanded(value) {}
 };
 
 /**