I stopped using most legacy extensions a while back when I found Firefox was faster and more stable without them. So, this change only affects me for the bette

I stopped using most legacy extensions a while back when I found Firefox was faster and more stable without them. So, this change only affects me for the better - ditching years of crufty "oh we have to do this super-kludgey thing because a couple big extensions rely on it" code so the whole thing can go multi-process and keep improving.