Clicking on a focusable element doesn't focus it

[jdm]

<style>div:focus { color: red; }</style>
<div tabindex=0 style="background-color: green; width: 100px; height: 100px;"><p>hello</p></div>
<button onclick="document.querySelector('div').focus()">focus</button>

The tabindex=0 makes the element focusable. In Firefox clicking on the element turns the text red; in Servo it does not.

[jdm]

Clicking on the rest of the page does make the div unfocused if it is focused, however.

[jdm]

Fixed by #26902.