chromium/third_party/blink/web_tests/external/wpt/html/semantics/interactive-elements/the-dialog-element/fixed-position-child-with-fo-ancestor.html

<!DOCTYPE html>
<html>
<title>Test that a fixed positioned child of a dialog is aligned to the viewport</title>
<head>
<link rel="match" href="fixed-position-child-with-fixed-position-cb-ref.html">
<link rel="help" href="https://fullscreen.spec.whatwg.org/#new-stacking-layer">
<style>
::backdrop {
    display: none;
}
#dialog {
    outline: none;
}
</style>
</head>
<body>
<svg>
  <foreignObject>
    <dialog id="dialog">
        Dialog should be centered.
        <div style="position: fixed; top: 0px; left: 0px">This fixed positioned element is aligned to viewport top-left.</div>
    </dialog>
  </foreignObject>
</svg>
<script>
dialog.showModal();
</script>
</body>
</html>