deprecated about:config entries

[jawz101]

security.tls.unrestricted_rc4_fallback
security.tls.insecure_fallback_hosts.use_static_list
deprecated in FFox 44
https://bugzilla.mozilla.org/show_bug.cgi?id=1165421
https://bugzilla.mozilla.org/show_bug.cgi?id=999544

media.gmp-eme-adobe.enabled
I don't even remember when they used an adobe plugin but FFox uses the widevine plugin at media.gmp-widevinecdm.enabled

datareporting.healthreport.service.enabled
is this even vaild?? I've just been checking all of these by right-clicking and resetting the pref. if the pref goes away (doesn't toggle) it's old or maybe an undocumented preference I guess :/

loop.facebook.shareUrl
loop.logDomains
social integration was disabled a while ago

[Atavic]

datareporting.healthreport.service is deprecated from FF46:
arkenfox/user.js#123

[Thorin-Oakenpants]

if the pref goes away (doesn't toggle) it's old or maybe an undocumented preference I guess

Some preferences are "hidden preferences". To be absolutely sure a preference is deprecated/removed you need to confirm it from the source (bugzilla) and check the source (DXR central)

But to save you time, earthlng and I did it all for you - see Atavic's link above

I don't even remember when they used an adobe plugin

Adobe's EME (Encryption Media Extension) is a CDM (Content Decryption Module) GMP (Gecko Media Plugin) just the same as Widevine is.