[DevTools] Make UI.GlassPane position contentElement for different overlay controls.

third_party/WebKit/Source/devtools/front_end/quick_open/FilteredListWidget.js

 /*
  * Copyright (c) 2012 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.
  */
 /**
  * @unrestricted
  * @implements {UI.ListDelegate}
  */
 QuickOpen.FilteredListWidget = class extends UI.VBox {
@@ skipping 101 matching lines @@
     if (ranges) {
       UI.highlightRangesWithStyleClass(element, ranges, 'highlight');
       return true;
     }
     return false;
   }
 
   showAsDialog() {
     this._dialog = new UI.Dialog();
     this._dialog.setWrapsContent(true);
-    this._dialog.setPosition(undefined, 22);
+    this._dialog.setPosition(null, 22);
     this.show(this._dialog.element);
     this._dialog.show();
     this._updateShowMatchingItems();
   }
 
   /**
    * @return {string}
    */
   _value() {
     return this._prompt.text().trim();
@@ skipping 406 matching lines @@
   /**
    * @return {string}
    */
   notFoundText() {
     return Common.UIString('No results found');
   }
 
   dispose() {
   }
 };