MD Settings: Potential <dialog> close focus workaround, WIP

ui/webui/resources/cr_elements/cr_dialog/cr_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 'cr-dialog' is a component for showing a modal dialog. If the
  * dialog is closed via close(), a 'close' event is fired. If the dialog is
  * canceled via cancel(), a 'cancel' event is fired followed by a 'close' event.
  * Additionally clients can inspect the dialog's |returnValue| property inside
  * the 'close' event listener to determine whether it was canceled or just
@@ skipping 25 matching lines @@
     // If the active history entry changes (i.e. user clicks back button),
     // all open dialogs should be cancelled.
     window.addEventListener('popstate', function() {
       if (!this.ignorePopstate && this.open)
         this.cancel();
     }.bind(this));
   },
 
   cancel: function() {
     this.fire('cancel');
-    HTMLDialogElement.prototype.close.call(this, '');
+    this.close('');
   },
 
   /**
    * @param {string=} opt_returnValue
    * @override
    */
   close: function(opt_returnValue) {
-    HTMLDialogElement.prototype.close.call(this, 'success');
+    var returnValue = opt_returnValue == '' ? opt_returnValue : 'success';
+    // Moving the focus to a child of |this| that resides outside the
+    // |this.shadowRoot| seems to cause the focus to not be lost.
+    this.querySelector('paper-button').focus();
+    HTMLDialogElement.prototype.close.call(this, returnValue);
   },
 
   /** @return {!PaperIconButtonElement} */
   getCloseButton: function() {
     return this.$.close;
   },
 });