We were keeping an unbounded list of MotionEvents inside of the
FalsingManager. Generally, this list should have shrunk itself
periodically, but in practice it only shrank itself when someone
double taps a notification.
Meanwhile, we weren't even using the data in the list!
With this change, we only keep the current and prior list of
MotionEvents - the ones we actually use. The list of historical
events is removed, so the leak goes with it.
Fixes: 177329773
Test: atest SystemUITests && manual
Change-Id: If8bfeea944850d972434915018b5bbfb3acb80e4
7da60de090