 isn't as easy. We can't rely on touch events at the
player level, because a tap (touchstart + touchend) on the video itself on
mobile devices is meant to turn controls off (and on). User activity is
checked asynchronously, so what could happen is a tap event on the video
turns the controls off, then the touchend event bubbles up to the player,
which if it reported user activity, would turn the controls right back on.
(We also don't want to completely block touch events from bubbling up)
Also a touchmove, t