chromium/third_party/blink/web_tests/fast/xmlhttprequest/xmlhttprequest-sync-disabled.html

<!DOCTYPE html>
<html>
<head>
    <script src="../../resources/js-test.js"></script>
    <script>
        if ('internals' in window) {
            internals.settings.setSyncXHRInDocumentsEnabled(false);
        } else {
            document.write('This test depends on the syncXHRInDocumentsEnabled setting being false, so run in DumpRenderTree or manually enable it');
        }

        description('This tests that synchronous XMLHttpRequests fail when they are disabled for documents.');
        var xhr = new XMLHttpRequest();
        shouldThrow('xhr.open("GET", "http://mydomain/", false)');
    </script>
</head>
<body>
    <div id="description"></div>
    <div id="console"></div>
</body>
</html>