Fixes #19709 (closed).
We've long removed the tap highlight, but that takes away from some decent accessibility friendliness. This removes that code so that the highlight is restored to tap targets. It only appears on the tap, disappearing after you release.
/x-ref: https://github.com/necolas/normalize.css/issues/23 where they discuss it's removal in https://github.com/necolas/normalize.css/commit/09be23f8320602edd343e55bbaf4ebc02550b1cc. I'm guessing we just left our implementation intact.