Support predicted and coalesced events

[smaug----]

Some of the Pointer Events features need to be tested manually since it isn't really possible to have automated tests for coalesced, and especially predicted events: https://w3c.github.io/pointerevents/#coalesced-and-predicted-events

[whimboo]

@smaug---- referred to https://github.com/w3c/pointerevents/pull/390 which got the feature added that cannot be tested right now.