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

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

Index: chrome/browser/resources/settings/people_page/password_prompt_dialog.js
diff --git a/chrome/browser/resources/settings/people_page/password_prompt_dialog.js b/chrome/browser/resources/settings/people_page/password_prompt_dialog.js
index 2625f2ba6195b916f413eee1bed0a54f0b003676..7bbb914fd5300cd63c563fa22a472c5a68622bb9 100644
--- a/chrome/browser/resources/settings/people_page/password_prompt_dialog.js
+++ b/chrome/browser/resources/settings/people_page/password_prompt_dialog.js
@@ -97,30 +97,13 @@ Polymer({
 
   /** @override */
   attached: function() {
+    this.writeUma_(LockScreenProgress.START_SCREEN_LOCK);
+    this.$.dialog.showModal();
     this.async(function() {
       this.$.passwordInput.focus();
     }.bind(this));
   },
 
-  /**
-   * Open up the dialog. This will wait until the dialog has loaded before
-   * opening it.
-   */
-  open: function() {
-    // Wait until the dialog is attached to the DOM before trying to open it.
-    var dialog = /** @type {{isConnected: boolean}} */ (this.$.dialog);
-    if (!dialog.isConnected) {
-      setTimeout(this.open.bind(this));
-      return;
-    }
-
-    if (this.$.dialog.open)
-      return;
-
-    this.writeUma_(LockScreenProgress.START_SCREEN_LOCK);
-    this.$.dialog.showModal();
-  },
-
   /** @private */
   onCancelTap_: function() {
     if (this.$.dialog.open)