chromium/src/third_party/blink/web_tests/security/srcdoc-include-file.html

<!--
  iframe using the srcdoc URL must be able to load files subresources if the
  iframe was created from a file. This should continue to be true after history
  navigations. See https://crbug.com/949510.
-->
<script src="../resources/testharness.js"></script>
<script src="../resources/testharnessreport.js"></script>

<iframe name="theiframe" srcdoc="
  <script src='./resources/script.js'
          onload='parent.window.onScriptLoaded();'>
  </script>
"></iframe>

<a target="theiframe" href="../resources/back.html"></a>

<script>
  let button = document.querySelector("a");
  let iframe = document.querySelector("iframe");

  let scriptLoaded = function() {
    return new Promise(resolved => window.onScriptLoaded = resolved);
  };

  promise_test(async function(t) {
    // 1. Check file subresource can be loaded from the initial about:srcdoc
    //    document.
    await scriptLoaded();
    button.click();
    // 2. Check file subresource can be loaded again after a new navigation to
    //    about:srcdoc.
    await scriptLoaded();
  });
</script>