src/third_party/devtools/front_end/toolbox_bootstrap/Toolbox.js

// Copyright 2014 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.
(function() {
  /**
   * @suppressGlobalPropertiesCheck
   */
  function toolboxLoaded() {
    if (!window.opener) {
      return;
    }
    const app = window.opener['Emulation']['AdvancedApp']['_instance']();
    app['toolboxLoaded'](document);
  }

  runOnWindowLoad(toolboxLoaded);
})();