No slider handle focus outlines in WordPress 4.3.1

The slider handles do not have focus outlines for accessibility when clicking or tabbing on a clean install of WordPress 4.3.1. I tried adjusting the CSS outline property with no success. You can see somewhat of a blue square in the middle of the center handle when clicked or focused using the tab key.

Reproduced issue in the latest versions of Chrome, Safari, Firefox, and Edge with a clean install of WordPress 4.3.1 and enqueuing the script using the 'iris' handle.


Reproduce the issue in a clean WordPress 4.3.1 install using the script enqueued with the “iris” handle, then inspect how Iris renders and styles slider-handle focus states. Done means keyboard and click focus produce a clear outline on every slider handle in the listed browsers.

Written by the indexing model from the issue text.