third_party/WebKit/LayoutTests/editing/inserting/line-break.html

<script>
if (window.testRunner) {
    testRunner.dumpEditingCallbacks();
    testRunner.dumpAsLayoutWithPixelResults();
}
</script>
<p>This testcase used to break InsertLineBreak.  The editable region below should have two empty paragraphs in it, and the caret should be in the second.</p>

<div id="test" contenteditable="true"><div>
<br></div></div>

<script>
var s = window.getSelection();
var e = document.getElementById("test");

s.collapse(e, 0);
document.execCommand("InsertLineBreak");

</script>