Specify the event lifecycle/event loop

[dtapuska]

We should decided where the event loop should be specified (either in houdini or the HTML spec).

The timing of when events are handled respective to when rAF runs is important.

Relevant links are:
https://github.com/atotic/event-loop
whatwg/html#1927
w3c/pointerevents#9

[RByers]

Also IIRC Ojan presented his Browser Rendering Pipeline doc at the very first Houdini meeting as one of the things we needed to do to really "explain" the web.

[domenic]

Is this worklets related? Worklet event loops are specified in good detail now, but I think this might be more general...