FF61 introduced quite a few changes, including removing the ability to set a blank startpage in the UI, and a new Home options tab with unified Activity Stream (AS) defaults and dropdown options. Because the only way to stop AS on startup is to enforce a blank page (pref 0102), and setting this auto changes `home+newwindow` (0103) and `newtab` (0104) to a blank page, then we're just going to go ahead and enforce that on all of them.
For more info see the discussion in #426
Both deprecated in FF61, but we'll remove them from the user.js
- `services.blocklist.signing.enforced` is default true since FF50
- `browser.storageManager.enabled` only controls "Site Data" UI visibility
2732 was just enforcing default since at least FF52, and 2733 has never been used, was only there for info. Offline Cache or appCache (2730) is already behind a prompt (2731), and is already limited (in FF60+) to HTTPS (2730b).
Note: I am not 100% sure what happens with an app update. If this is divorced from that check now, you should be able to get FF updated without any system addons. We'll have to wait until 62 needs an update to test it. In the meantime I've edited the [NOTE]. I've also left this inactive (eg imagine if they pushed a critical update for formfill), so this is an end-user decision. Added to sticky to revisit this pref
I see no point in keeping this to enforce a default that FF itself doesn't use - see https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/User-Agent/Firefox
- "... is an optional compatibility token that some Gecko-based browsers may choose to incorporate, to achieve maximum compatibility with websites that expect Firefox"
