Migrate <cr-dialog> from PaperDialogBehavior to native <dialog>.

chrome/browser/resources/settings/certificate_manager_page/certificates_error_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 A dialog for showing SSL certificate related error messages.
  * The user can only close the dialog, there is no other possible interaction.
  */
 Polymer({
   is: 'settings-certificates-error-dialog',
 
   properties: {
     /** @type {!CertificatesError|!CertificatesImportError} */
     model: Object,
   },
 
   /** @override */
   attached: function() {
-    /** @type {!CrDialogElement} */ (this.$.dialog).open();
+    /** @type {!CrDialogElement} */ (this.$.dialog).showModal();
   },
 
   /** @private */
   onOkTap_: function() {
     /** @type {!CrDialogElement} */ (this.$.dialog).close();
   },
 
   /**
    * @param {{name: string, error: string}} importError
    * @return {string}
    * @private
    */
   getCertificateErrorText_: function(importError) {
     return loadTimeData.getStringF(
         'certificateImportErrorFormat', importError.name, importError.error);
   },
 });