A tooltip triggered by hover and focus also fires on a tap, because tapping a
button focuses it. On a phone the hint then covers the thing that was just
pressed, and it stays there until something else takes focus. There is no
moment before a click for it to fill.
`IS_TOUCH_PRIMARY` reads `(hover: none)` once at load, the way `IS_MAC` reads
the platform, and the tooltip renders its trigger bare when it is set.
Daniel Hiller
764bd106a7