third_party/WebKit/LayoutTests/editing/inserting/editable-inline-element.html

<p>This tests InsertParagraph inside an editable inline element.</p>
<div style="border: 1px solid red;"><span id="span" contenteditable="true">foo</span></div>

<script>
var sel = window.getSelection();
var span = document.getElementById("span");

sel.collapse(span, 0);
document.execCommand("InsertParagraph");
</script>