MD Settings: Eliminate use of ES6 for Chrome OS

ui/webui/resources/cr_elements/network/cr_network_icon.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 rendering network icons based on ONC
  * state properties.
  */
 
 Polymer({
@@ skipping 66 matching lines @@
    */
   showTechnology_: function() {
     return this.getTechnology_() != '';
   },
 
   /**
    * @return {string}
    * @private
    */
   getTechnology_: function() {
-    let networkState = this.networkState;
+    var networkState = this.networkState;
     if (!networkState)
       return '';
-    let type = networkState.Type;
+    var type = networkState.Type;
     if (type == CrOnc.Type.WI_MAX)
       return 'network:4g';
     if (type == CrOnc.Type.CELLULAR && networkState.Cellular) {
-      let technology =
+      var technology =
           this.getTechnologyId_(networkState.Cellular.NetworkTechnology);
       if (technology != '')
         return 'network:' + technology;
     }
     return '';
   },
 
   /**
    * @param {string|undefined} networkTechnology
    * @return {string}
@@ skipping 22 matching lines @@
         return 'badge-3g';
     }
     return '';
   },
 
   /**
    * @return {boolean}
    * @private
    */
   showSecure_: function() {
-    let networkState = this.networkState;
+    var networkState = this.networkState;
     if (!this.networkState)
       return false;
     if (networkState.Type == CrOnc.Type.WI_FI && networkState.WiFi) {
-      let security = networkState.WiFi.Security;
+      var security = networkState.WiFi.Security;
       return !!security && security != 'None';
     }
     return false;
   },
 });