Iframed Flutter hogs focus

It seems that focus cannot be taken OUT of an iframed flutter app. Compare with commented-out code to see the expected behavior.

by David Iglesias

HTML

<div>
  <div>
    <input tabindex=0 type="text" value="Click here, press Tab" />
  </div>
<iframe tabindex=0 src="https://dit-tests.web.app" frameborder="0"></iframe>
<!--
    <iframe tabindex=0 src="https://fiddle.jshell.net/ditman/a0Luh1zq/show/light/" frameborder="0"></iframe>
-->
<div>
    <input tabindex=0 type="text" value="unreachable via Tab" />
  </div>
</div>

CSS

iframe {
  width: 320px;
  height: 200px;
  margin: 16px 0px;
  border: inset;
}

JavaScript

function focusEvt(e) {
  console.log(e.type)
  console.log('target', e.target);
  console.log('related', e.relatedTarget);
  console.log('---');
}

window.addEventListener('focus', focusEvt);
window.addEventListener('blur', focusEvt)
window.addEventListener('focusout', focusEvt);
window.addEventListener('focusin', focusEvt);