check: safer flips vs webextensions / privileged
just a reminder to follow up this (because of https://github.com/arkenfox/user.js/issues/1727 - boring don't read, really, ignore it)
So we flip a bunch of APIs off in safer mode - can we please check/upstream-if-needed all of these do not affect web ext (or privileged content). IIUIC for a long time we've chipped away at these, e.g. pdfs, some about pages, etc. Recently RFP has been exempted from web exts (I think it took some extra principal parsing, IANAEngineer)
So this would be nice to check and fixup anything if needed