MD Settings: Users: Fix add person validation and dialog focus

chrome/browser/resources/settings/people_page/users_add_user_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.
 
 /**
  * @fileoverview
  * 'settings-users-add-user-dialog' is the dialog shown for adding new allowed
  * users to a ChromeOS device.
  */
 (function() {
@@ skipping 14 matching lines @@
  *     e.g. 'john@chromium.org'
  * @const {!RegExp}
  */
 var EMAIL_REGEX = new RegExp(
     '^\\s*([\\w\\.!#\\$%&\'\\*\\+-\\/=\\?\\^`\\{\\|\\}~]+)@' +
     '([A-Za-z0-9\-]{2,63}\\..+)\\s*$');
 
 Polymer({
   is: 'settings-users-add-user-dialog',
 
+  properties: {
+    /** @private */
+    isValid_: {
+      type: Boolean,
+      value: false,
+    },
+  },
+
   open: function() {
+    this.isValid_ = false;
     this.$.dialog.showModal();
   },
 
   /** @private */
   onCancelTap_: function() {
     this.$.dialog.cancel();
   },
 
   /**
    * Validates that the new user entered is valid.
    * @private
    * @return {boolean}
    */
   validate_: function() {
     var input = this.$.addUserInput.value;
-    var valid = NAME_ONLY_REGEX.test(input) || EMAIL_REGEX.test(input);
-
-    this.$.add.disabled = !valid;
-    this.$.addUserInput.invalid = !valid;
-    return valid;
+    this.isValid_ = NAME_ONLY_REGEX.test(input) || EMAIL_REGEX.test(input);
+    return this.isValid_;
   },
 
   /** @private */
   addUser_: function() {
     // May be submitted by the Enter key even if the input value is invalid.
     if (!this.validate_())
       return;
 
     var input = this.$.addUserInput.value;
 
@@ skipping 10 matching lines @@
 
     chrome.usersPrivate.addWhitelistedUser(
         userEmail,
         /* callback */ function(success) {});
     this.$.addUserInput.value = '';
     this.$.dialog.close();
   },
 });
 
 })();