md-settings: wrap lock screen dialogs in dom-if.

chrome/browser/resources/settings/people_page/setup_fingerprint_dialog.js

 // Copyright 2017 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.
 
 cr.exportPath('settings');
 
 /**
  * The steps in the fingerprint setup flow.
  * @enum {number}
  */
@@ skipping 61 matching lines @@
   tapSensorMessageTimeoutId_: 0,
 
   /** @private {?settings.FingerprintBrowserProxy}*/
   browserProxy_: null,
 
   /** @override */
   attached: function() {
     this.addWebUIListener(
         'on-fingerprint-scan-received', this.onScanReceived_.bind(this));
     this.browserProxy_ = settings.FingerprintBrowserProxyImpl.getInstance();
-  },
 
-  /**
-   * Opens the dialog.
-   */
-  open: function() {
     this.$.arc.clearCanvas();
     this.$.arc.drawBackgroundCircle();
     this.$.arc.drawShadow(10, 0, 0);
     this.browserProxy_.startEnroll();
     this.$.dialog.showModal();
   },
 
   /**
    * Closes the dialog.
    */
@@ skipping 181 matching lines @@
    */
   onAddAnotherFingerprint_: function() {
     this.fire('add-fingerprint');
     this.reset_();
     this.$.arc.drawBackgroundCircle();
     this.$.arc.drawShadow(10, 0, 0);
     this.browserProxy_.startEnroll();
   },
 });
 })();