While debugging T112552, we discovered that mw.loader.inspect() on Safari and Firefox might throw exceptions for several types of CSS selectors.
The exception is a DOM Exception 12 SyntaxError.
The first cause of this was document.querySelector() being fed with actual invalid CSS queries on Commons.
The second cause is a bug/undefined behavior for vendor prefixed pseudo elements.
- Webkit fails on all of these
- Firefox throws an exception on vendor prefixes other than their own
- Chrome throws an exception on vendor prefix other than their own.