I don't understand the goal of multiprocess. It's for faggots who can't deal with multithreading, and fags up the process list, with no easy way to tell how much memory the browser in total is taking up.
Firefox still has never gotten its head out of its ass in terms of showing which tab or process is sucking CPU or memory, so they're just going to bail and defer to the OS, because they're failures who can't write a decent integrated system.
Mozilla is a pile of cock sucking Google-fawning retards who are more interested in playing "Me Too!" with browser bling than they are actually solving the problems of web browsers. Fuck them.