WebUI: Undo some usages of ES6 features that break uglify.

chrome/browser/resources/settings/site_settings/cookie_tree_behavior.js

 // Copyright 2015 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.
 
 /**
  * @fileoverview A behavior for managing a tree of cookies.
  */
 
 /** @polymerBehavior */
 var CookieTreeBehaviorImpl = {
@@ skipping 30 matching lines @@
     var loadChildrenRecurse = function(childList) {
       var parentId = childList.id;
       var children = childList.children;
       var prefix = '';
       if (parentId !== null) {
         this.rootCookieNode.populateChildNodes(parentId,
             this.rootCookieNode, children);
         prefix = parentId + ', ';
       }
       var promises = [];
-      for (let child of children) {
+      for (var i = 0; i < children.length; i++) {
+        var child = children[i];
         if (child.hasChildren) {
           promises.push(this.browserProxy.loadCookieChildren(
               prefix + child.id).then(loadChildrenRecurse.bind(this)));
         }
       }
       return Promise.all(promises);
     }.bind(this);
 
     // New root being added, clear the list and add the nodes.
     this.sites = [];
@@ skipping 28 matching lines @@
    * @return {Promise}
    */
   removeAllCookies: function() {
     return this.browserProxy.removeAllCookies().then(
         this.loadChildren_.bind(this));
   },
 };
 
 /** @polymerBehavior */
 var CookieTreeBehavior = [SiteSettingsBehavior, CookieTreeBehaviorImpl];