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chromium/third_party/blink/web_tests/http/tests/inspector-protocol/network/resources/xhr-iframe-auth-fail.html 

<!DOCTYPE html>
<html>
<head>
<script>
var xhr = new XMLHttpRequest();
xhr.onload = function() {
  console.log('xhr.status = ' + xhr.status);
};
// Suppress usage of credentials cached from other tests in pre-emptive auth by adding a bogus user to the URL.
xhr.open("GET", "http://[email protected]:8000/inspector-protocol/network/resources/unauthorised.pl");
xhr.send();
</script>
</head>
</html>