1166315 - Support easy extension of protocol.js actors

Status: NEW

(DevTools :: Framework, defect)

Description

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

In bug 1036949, Honza's adding a way to extend NodeActor.form from add-ons.  

Instead of having to add such an API for every possible actor method of interest to add-ons,  I was imagining that protocol.js could offer a kind of "filtering extension" API as part of every protocol.js actor.  Using this case, as an example:

1. Add-on registers that it wants to filter "NodeActor.form"
2. Each time NodeActor.form is called, protocol.js also calls the add-on's code, giving it a chance to extend / modify the result

It's not specific to forms or NodeActor at all, as this would be available for any protocol.js supported method.  It would support any number of filtering users / add-ons that want to override the same thing.