Lack of interaction event specification

[annevk]

There's many places in HTML that mention "interaction event" in a comment indicating a lack of integration and clarity with regards to the processing model of what's being defined. I'd like this to be a canonical issue for those issues.

Background:

• https://lists.w3.org/Archives/Public/www-tag/2014Apr/0035.html
• Specify the Event Loop integration for various non-deprecated events, incl. hit testing w3c/uievents#23

[dtapuska]

Issue w3c/pointerevents#9 is also relevant.

In Chrome we are working to aligning some of the events relative to rAF so the timing of these events is also important to specify. I've tried to capture some of the model here: atotic/event-loop#1