chromium/third_party/blink/web_tests/external/wpt/html/browsers/origin/inheritance/about-blank-iframe.html

<!doctype html>
<html>
  <head>
    <title>about:blank in child browsing context aliases security origin</title>
    <script src="/resources/testharness.js"></script>
    <script src="/resources/testharnessreport.js"></script>
  </head>
  <body>
    <script>
      test(() => {
        let iframe = document.createElement('iframe');
        document.body.appendChild(iframe);
        // Should not throw: srcdoc should always be same-origin.
        iframe.contentWindow.document.body.innerHTML = '<p>Hello world!</p>';

        // Explicitly set `domain` component of origin: any other same-origin
        // browsing contexts are now cross-origin unless they also explicitly
        // set document.domain to the same value.
        document.domain = document.domain;
        // Should not throw: the origin should be aliased, so setting
        // document.domain in one Document should affect both Documents.
        assert_equals(
            iframe.contentWindow.document.body.textContent,
            'Hello world!');
      });
    </script>
  </body>
</html>