When the spec says to:
   queue a task to do X and do Y
it's unclear whether to parse that as
   queue a task to (do X and do Y)
or
   (queue a task to do X) and (do Y)

(E.g., 4.8.10.6 "Offsets into the media resource" has:
    the user agent may queue a task to remove the track ...
    and then fire a trusted event ...
Is the event fired inside the task or outside?)

I think the former interpretation is usually intended,
but I'm also pretty sure that the latter is sometimes intended
(e.g., when "do Y" = "abort these steps" or when it queues another task).

To clarify, you could use a well-placed "first":
   queue a task to first do X. and then do Y
vs
   first queue a task to do X, and then do Y