MD Settings: Eliminate use of ES6 for Chrome OS

chrome/browser/resources/settings/internet_page/network_ip_config.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 Polymer element for displaying the IP Config properties for
  * a network state. TODO(stevenjb): Allow editing of static IP configurations
  * when 'editable' is true.
  */
 Polymer({
@@ skipping 122 matching lines @@
    * @param {!CrOnc.IPConfigProperties|undefined} ipconfig
    * @return {!CrOnc.IPConfigUIProperties} A new IPConfigUIProperties object
    *     with RoutingPrefix expressed as a string mask instead of a prefix
    *     length. Returns an empty object if |ipconfig| is undefined.
    * @private
    */
   getIPConfigUIProperties_: function(ipconfig) {
     var result = {};
     if (!ipconfig)
       return result;
-    for (let key in ipconfig) {
-      let value = ipconfig[key];
+    for (var key in ipconfig) {
+      var value = ipconfig[key];
       if (key == 'RoutingPrefix')
         result.RoutingPrefix = CrOnc.getRoutingPrefixAsNetmask(value);
       else
         result[key] = value;
     }
     return result;
   },
 
   /**
    * @param {!CrOnc.IPConfigUIProperties} ipconfig The IP Config UI properties.
    * @return {!CrOnc.IPConfigProperties} A new IPConfigProperties object with
    *     RoutingPrefix expressed as a a prefix length.
    * @private
    */
   getIPConfigProperties_: function(ipconfig) {
     var result = {};
-    for (let key in ipconfig) {
-      let value = ipconfig[key];
+    for (var key in ipconfig) {
+      var value = ipconfig[key];
       if (key == 'RoutingPrefix')
         result.RoutingPrefix = CrOnc.getRoutingPrefixAsLength(value);
       else
         result[key] = value;
     }
     return result;
   },
 
   /**
    * @return {boolean}
@@ skipping 29 matching lines @@
     var field = event.detail.field;
     var value = event.detail.value;
     // Note: |field| includes the 'ipv4.' prefix.
     this.set('ipConfig.' + field, value);
     this.fire('ip-change', {
       field: 'StaticIPConfig',
       value: this.getIPConfigProperties_(this.ipConfig_.ipv4)
     });
   },
 });