[wsha]

Electrolysis is mostly already implemented with the XUL version of Firefox and many add-ons have been ported over to be compatible with it.

The main new change being announced recently (electrolysis and extension signing have been known about for a while now) is the deprecation of XUL in the browser in general and for add-ons in particular and the adoption of a new extension API's that are more limited in functionality (WebExtensions and whatever else they decide to do to allow more functionality than is available in Chrome). There are security implications to these changes but multi-process Firefox is not the main driver. Mozilla is giving up on XUL in favor of HTML and using this as a pretext to limit the functionality of add-ons (which many Firefox developers have wanted to do for a long time for security and stability reasons).