Focus outlines not working

Created by: hnrch02

If you tab to the checkbox in this Bin, you will see that focus outlines are not working. Only the minified CSS is affected, so I traced the problem back to clean-css.

If I give clean-css this

div {
  outline: 5px auto -webkit-focus-ring-color;
}

it gives me back this

div{outline:-webkit-focus-ring-color 5px}

removing auto from the property and rendering focus outlines (at least in WebKit) non-existent.

/cc @mdo @cvrebert @XhmikosR