ChromeOS MD-OOBE: Add Timezone Selection screen.

chrome/browser/resources/chromeos/login/oobe_welcome_dialog.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.
 
 Polymer({
   is: 'oobe-welcome-dialog',
   properties: {
     /**
      * Currently selected system language (display name).
      */
     currentLanguage: {
       type: String,
       value: '',
     },
+    /**
+     * Controls visibility of "Timezone" button.
+     */
+    timezoneButtonVisible: {
+      type: Boolean,
+      value: false,
+    },
   },
 
   onLanguageClicked_: function() {
     this.fire('language-button-clicked');
   },
 
   onAccessibilityClicked_: function() {
     this.fire('accessibility-button-clicked');
   },
 
+  onTimezoneClicked_: function() {
+    this.fire('timezone-button-clicked');
+  },
+
   onNextClicked_: function() {
     this.fire('next-button-clicked');
   }
 });