@Mossop @erikvold I think you guys both missing a point I'm trying to make both `filter` and `browser/events` etc.. just return plain event target (nothing new) and use `event/core` `on / emit` functions to dispatch on these
results. So if we are sure that `event/core` preserves FIFO order of things that register listeners to it, there is
no point of testing all the users that just return event target to which you use `event/core` to subscribe.

Here is how in test **filtered** event stream -> `browser/events` is being listened to. Via tested `event/core#on`:
https://github.com/Gozala/addon-sdk/blob/bug/tab-detraitifaction%40854980/test/test-browser-events.js#L16

And here is how **filter** just forwards values using tested `event/core#emit` to dispatch the result of filter(...)
that is used above.
https://github.com/Gozala/addon-sdk/blob/bug/tab-detraitifaction%40854980/lib/sdk/event/utils.js#L36

Since non of these do introduce anything new for event dispatch and just use tested building blocks do we
still wanna retest those here ?