[kibwen]

Mozilla's test pilot projects there serve to prototype proposed extension APIs. It's there to inform the design of what hooks are needed to make such an addon possible, so that it will still be possible in a world with only WebExtensions.

[icebraining]

Are the APIs required to make TabCenter as a WebExtension guaranteed to work on FF 57? If not, temgo is still right, no? At least an argument could be made that the elimination of XUL should only happen when the current experiments can actually be implemented using the new model.