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

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

Index: chrome/browser/resources/settings/people_page/setup_pin_dialog.js
diff --git a/chrome/browser/resources/settings/people_page/setup_pin_dialog.js b/chrome/browser/resources/settings/people_page/setup_pin_dialog.js
index bd4f1e7514b544c6468ca3b786c5148cc0d6f6c4..a27966227d1b603bbf2ad3e3b6093bd76b707ef6 100644
--- a/chrome/browser/resources/settings/people_page/setup_pin_dialog.js
+++ b/chrome/browser/resources/settings/people_page/setup_pin_dialog.js
@@ -7,8 +7,7 @@
  * 'settings-setup-pin-dialog' is the settings page for choosing a PIN.
  *
  * Example:
- *
- * <settings-setup-pin-dialog set-modes="[[quickUnlockSetModes]]">
+ * * <settings-setup-pin-dialog set-modes="[[quickUnlockSetModes]]">
  * </settings-setup-pin-dialog>
  */
 
@@ -101,11 +100,7 @@ Polymer({
   /** @override */
   attached: function() {
     this.resetState_();
-  },
-
-  open: function() {
     this.$.dialog.showModal();
-    this.$.pinKeyboard.focus();
   },
 
   close: function() {
@@ -276,7 +271,8 @@ Polymer({
       }
 
       this.resetState_();
-      this.fire('done');
+      if (this.$.dialog.open)
+        this.$.dialog.close();
     }
 
     this.setModes.call(