chrome/test/data/extensions/api_test/executescript/permissions/frames.js

// Copyright 2011 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// document.write is not pretty, but it saves us from having to wait for the
// DOM to load before adding iframes.  This means one less callback to wait on.
function addIFrame(host) {
  document.write(
      `<iframe src="http://${host}:${location.port}` +
      '/extensions/api_test/executescript' +
      '/permissions/empty.html"> </iframe>');
}
addIFrame('a.com');
addIFrame('b.com');
addIFrame('c.com');