Clarify some things regarding onbefore* events

[hallvors]

Per IRC discussion with Anne:

7:59 PM <hallvors> it's up to the UA when to fire them, but typically it would happen for example when the user opens the "Edit" menu
7:59 PM <annevk> ah right, they're unrelated to firing of the non-before events
8:00 PM <hallvors> so the UA is about to show the user a menu containing "copy"/"cut"/"paste" commands, and wants to enable or disable them
8:00 PM <hallvors> exactly. They are sort of completely unrelated to those other clipboard events..
8:00 PM <annevk> so what you actually want to define then is a set of steps for displaying "edit UI"
8:00 PM <annevk> And then you have an algorithm whenever you "display edit UI"
8:01 PM <annevk> To figure out how you display it
8:01 PM <annevk> It happens to run some script from a queued task to figure that out
8:01 PM <annevk> Do you get distinct tasks for each event? Or do they share a task?
8:01 PM <annevk> That's the kind of thing that should be obvious from that algorithm

[hallvors]

I killed those before* events completely.