The names are probably less familiar, but more consistent:
- FrameCallback: a callback that is relative to the frame and wants the
frame offset (a duration) as argument.
- addXFrameCallback: adds the given callback to the internal lists/maps.
- scheduleXFrameCallback (currently only X = ""): add the callback, but
also trigger a new frame.
- handleX: the method that is invoked when the event-loop or the frame
calls into the scheduler.
- ensureXYZ: ensure that the callback happens.
Unfortunately there is the ambiguity between a "callback": it can be a
closure, or the action of doing a callback, so we end up with:
ensureBeginFrameCallback, and ensureEventLoopCallback, where
"callback" means the action of being called back.
