Wikimedia Bugzilla is closed!

The function fixDeprecatedAttributes from Santizer.php should add a CSS class to changed tags.
Usecase:
A user wants to fix all usage of deprecated attributes. To find them, he puts

li[type] {outline: 2px solid red;}

into his common.css.

This doesn't work when the attributes are automatically converted to CSS.

If an extra class was added, the user could use

li.mw-deprecated-attr-type {outline: 2px solid red;}