Promise and EventListener ( progress/notify support in gorillascript promise )

[unc0]

Take this code as an example. Sometimes the value we need to return from a promise is in an EventListener.
I don't know how to wrap this IndexedDB request into promise in gorillascript.
The vow promise library also use this progress/notify pattern to fill a promise from an EventListener. Maybe we should have these macro/functions in jsprelude?