ChromeOS MD-OOBE: Disable duplicate 'connected' events.

chrome/browser/resources/chromeos/login/oobe_welcome.js

 // Copyright 2016 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 material design OOBE.
  */
 
 Polymer({
   is: 'oobe-welcome-md',
@@ skipping 204 matching lines @@
    * This gets called when a network enters the 'Connected' state.
    *
    * @param {!{detail: !CrOnc.NetworkStateProperties}} event
    * @private
    */
   onNetworkConnected_: function(event) {
     var state = event.detail;
     if (state.GUID != this.networkLastSelectedGuid_)
       return;
 
+    // Duplicate asynchronous event may be delivered to some other screen,
+    // so disable it.
+    this.networkLastSelectedGuid_ = '';
     this.onSelectedNetworkConnected_();
   },
 
   /**
    * This is called when user taps on network entry in networks list.
    *
    * @param {!{detail: !CrOnc.NetworkStateProperties}} event
    * @private
    */
   onNetworkListNetworkItemSelected_: function(event) {
@@ skipping 90 matching lines @@
    * containing Chromium callback name.
    *
    * @private
    * @param {!Event} event
    */
   onA11yOptionChanged_: function(event) {
     chrome.send(
         event.currentTarget.chromeMessage, [event.currentTarget.checked]);
   },
 });