Open chrome DevTools, under Audits you can Audit the present state or reload the page and Audit on Load
Then under Web Page Performance there's a section that says: "Remove unused CSS Rules
Now it when I used it, I saw that it was listing some css that I was using problem was at the present state it wasn't being used so if you're toggling classes then obviously it'll show it if the class is not currently applied.
BTW if that doesn't show up as far as I know It works in chrome canary. Also I don't remember if I enabled a flag for this. (I don't think so)
