Comment 1 for bug 1268782

The fix is easy, in _uinput.Touch.tap, add an argument press_duration=0.1, and pass it to the sleep between finger_down and finger_up. Then, also pass it on Pointer.click to the Touch backend.

What's hard is the test for it. I think it wouldn't be correct to just check the value send to sleep. We need to check the amount of time elapsed between the _finger_down and _finger_up.