Suppose host has some three-finger gesture. Then we get the following sequence
of events:
DOWN-DOWN-DOWN-MOTION-CANCEL
Note that there is no UP in this sequence. So if we don't handle CANCEL then
we end up thinking that fingers are still touching the screen. Ideally we
should inform the application that cancel has happened as not to trigger
spurious taps but still this is way better than being stuck with phantom
finger touch.
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