MD Settings: Eliminate use of ES6 for Chrome OS

chrome/browser/resources/settings/internet_page/network_ip_config.js

Index: chrome/browser/resources/settings/internet_page/network_ip_config.js
diff --git a/chrome/browser/resources/settings/internet_page/network_ip_config.js b/chrome/browser/resources/settings/internet_page/network_ip_config.js
index 90b8e397cd0157b988c7c9c0b1b233827e85f082..b67955e8ada8c86823fefd2240260867a281d3c9 100644
--- a/chrome/browser/resources/settings/internet_page/network_ip_config.js
+++ b/chrome/browser/resources/settings/internet_page/network_ip_config.js
@@ -140,8 +140,8 @@ Polymer({
     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
@@ -158,8 +158,8 @@ Polymer({
    */
   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