chromium/third_party/blink/web_tests/editing/pasteboard/5761530-1.html

<div id="description">This tests to see that tabs are put into tab spans when they are copied individually.  The pasted tab should be inside of a tab span, not a style span.  To run the test manually, paste and then inspect the editable region, and ensure that there is a tab span at the beginning of the editable div.</div>
<div id="edit" contenteditable="true"><span style="white-space:pre;">	</span>xxx</div>
<script>
if (window.testRunner)
	testRunner.dumpAsText();
edit = document.getElementById("edit");

window.getSelection().collapse(edit, 0);
window.getSelection().modify("extend", "forward", "character");
document.execCommand("Copy");
window.getSelection().modify("move", "backward", "character");
document.execCommand("Paste");
if (window.testRunner)
    document.body.innerText = document.getElementById("description").innerText + "\n\n" + edit.innerHTML;
</script>