Tooltips functionality - Show on mobile only during touch state

So, the [tooltip spec](https://www.google.com/design/spec/components/tooltips.html#) specifically says:

> upon touch (without releasing) in a touch UI

Currently, we do it on touch and persist even through a scroll action. Any good way to come into alignment here?

We could listen on touchstart to show the tooltip and on touchend kill it. But, in testing this just now, Chrome and FF after a few seconds emit a [TouchCancel event](https://developer.mozilla.org/en-US/docs/Web/Events/touchcancel) which is due to them showing the context menu from the long-press. I have yet to find a direct solution to the problem as the "onContextMenu" event I'm seeing doesn't seem to fire at all, so can't cancel it that way.