chromium/chrome/test/data/extensions/platform_apps/web_view/background/webview_auth.html

<!--
Copyright 2016 The Chromium Authors
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.
-->
<!doctype html>
<script>
window.onmessage = function(e) {
  if (e.data.request == 'xhr') {
    var xhr = new XMLHttpRequest();
    xhr.open('GET', e.data.url);
    xhr.send();
  }
};
</script>