chromium/third_party/blink/web_tests/fast/forms/11423.html

<p>This tests to see that a line break inserted in a textarea is serialized as a '\n'.</p>
<textarea rows="5" id="textarea"></textarea>
<ul id="console"></ul>

<script>
function log(str) {
    var li = document.createElement("li");
    li.appendChild(document.createTextNode(str));
    var console = document.getElementById("console");
    console.appendChild(li);
}

if (window.testRunner)
    testRunner.dumpAsText();
    
var textarea = document.getElementById("textarea");
textarea.focus();
document.execCommand("InsertText", false, "foo");
document.execCommand("InsertLineBreak");
document.execCommand("InsertText", false, "bar");

if (textarea.value != "foo\nbar")
    log("Failure");
else
    log("Success");
</script>