Minor formatting issue: move InstanceTracker#restored attribute to top of class.

packages/apputils/src/instancetracker.ts

@@ -180,6 +180,13 @@ export class InstanceTracker<T extends Widget>
     return this._currentWidget;
   }
 
+  /**
+   * A promise resolved when the instance tracker has been restored.
+   */
+  get restored(): Promise<void> {
+    return this._restored.promise;
+  }
+
   /**
    * The number of widgets held by the tracker.
    */
@@ -368,13 +375,6 @@ export class InstanceTracker<T extends Widget>
     return values;
   }
 
-  /**
-   * A promise resolved when the instance tracker has been restored.
-   */
-  get restored(): Promise<void> {
-    return this._restored.promise;
-  }
-
   /**
    * Save the restore data for a given widget.
    *