This patch makes the dispatcher drop all of its state when it is
disabled (when the screen turns off). This ensures that the dispatcher
does not get stuck thinking a pointer is still down if the screen
turned off while the user was touching the display (such as a fat touch
while hitting the power button).
Bug: 3098344
Change-Id: If50ef5804870aa1acd3179fd4b40e3cda58dd39d
120a459485