chrome/test/data/extensions/api_test/active_tab/iframe.js

// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

function canXhr(url) {
  const xhr = new XMLHttpRequest();
  xhr.open('GET', url, false);
  let success = true;
  try {
    xhr.send();
  } catch (e) {
    assertEq('NetworkError', e.name);
    success = false;
  }
  return success;
}

document.addEventListener('DOMContentLoaded', function() {
  chrome.runtime.sendMessage({message: 'xhr'}, function(response) {
    const success = canXhr(response.url);
    chrome.runtime.sendMessage({success: success});
  });
});