<!DOCTYPE html>
<html>

<body>
    <input id="field" onbeforeinput=handleBeforeInput(event)></input>
    <script src="../../resources/dump-as-markup.js"></script>
    <script>
        Markup.description(`To manually test this, type some into the input field below and try to undo. The value of the text field should not change after attempting to undo.`);

        (function() {
            if (!window.internals || !window.eventSender || !window.testRunner)
                return;

            document.querySelector("#field").focus();

            eventSender.keyDown("a", []);
            eventSender.keyDown("b", []);
            eventSender.keyDown("c", []);
            Markup.dump("field", "initial value");

            testRunner.execCommand("Undo");
            Markup.dump("field", "after prevented undo");
        })();

        function handleBeforeInput(event)
        {
            if (event.inputType === "historyUndo")
                event.preventDefault();
        }
    </script>
</body>

</html>