Currently for motion events, monkey forces current system uptime onto both down time and event time. This breaks ACTION_MOVE events because the down time of it is supposed to be the time when finger is down. the new logic is: * check down time, if it's invalid (<0), fill in uptime * always update event time with a fresh uptime Bug: 6424997 Change-Id: I0b445815a5015d48c08bebc921c572164874449d