Consider removing process-model and max-processes setting
It most likely will not be possible to keep single process mode or even process count limits anymore, per https://chromium.googlesource.com/chromium/src/+/master/docs/security/side-channel-threat-model.md. We will likely need to remove these settings.
Some users (e.g. @hadess) will probably not be pleased as to the impact on memory. Creating a one-process-per-origin model in WebKit would be desirable as that would significantly reduce the number of processes we need.