I'm working my way through a profile of a cold Firefox startup taken via Procmon right now, and I noticed three
WriteFiles before startup finished via
PWRunnable. These are on a background thread pool, but cold startup on spinny disks is generally heavily IO bound, so regardless of where the IO happens it's a problem. Can we defer these until after startup, or is there a material risk of doing so in the event of, say, a startup crash? I feel like if we're setting a pref during startup where it's mission critical that we don't crash before we write it to disk, then that's a problem in itself.