Clear events when ACTION_CANCEL is present

When ACTION_CANCEL is present in the queue, we can clear the existing
events from the queue. This will also help pilfer pointers, because this
will allow extra time for the inputMonitor to pilfer pointers and
prevent unwanted behaviour.

Bug: 130352502
Test: open maps, then swipe from left or right. Observe that the map
does not shift in response to this gesture.

Change-Id: I6b3798f73da3dd26369d1d7887e24fde61333c31