focus-already-focused-iframe-inner.html

<!doctype html>
<meta charset="utf-8">
<title>Focus already focused iframe</title>
<script>
let haveGottenFocus = false;
function gotFocus() {
    if (haveGottenFocus) {
        parent.postMessage("FAIL", "*");
    } else {
        haveGottenFocus = true;
        parent.postMessage("focus", "*");
    }
}
window.onload = function() {
    document.getElementsByTagName("input")[0].focus();
}
</script>
<input onfocus="gotFocus();">

chromium/third_party/blink/web_tests/external/wpt/focus/support/focus-already-focused-iframe-inner.html