So that they can be enabled separately.

• Let layout.css.use-counters.enabled be independent from the unimplemented
  property counters.

• Always count in the style system (that is, always create
  Document::mStyleUseCounters), so that the warning from bug 1582374 works
  irrespective of these prefs.

• Add a pref check to the SVGElement code path so that the prefs properly
  reflect whether the histograms end up being recorded or not.

• Make the pref checks consistent (check both when reporting telemetry, not
  earlier).

https://hg.mozilla.org/mozilla-central/rev/ec8953817ef0
https://hg.mozilla.org/mozilla-central/rev/fea9c97d5004

Comment on attachment 9094392 [details]
Bug 1582814 - followup: fix a test now that we always count in the style system.

Beta/Release Uplift Approval Request

• User impact if declined: See bug 1578661 comment 51.
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: Bug 1578661
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Just shuffles the prefs so that we can enable just the use counters that the webcompat team needs.
• String changes made/needed: none

Comment on attachment 9094392 [details]
Bug 1582814 - followup: fix a test now that we always count in the style system.

OK for uplift for beta 10. This is work for the webcompat use counters experiment in beta/release 70.

Got conflict while uplifting to beta:

raul@raul-VirtualBox ~/mozilla-unified beta(0) $ hg graft -er ec8953817ef0::fea9c97d5004
grafting 567820:ec8953817ef0 "Bug 1582814 - Let the CSS use counter prefs be independent. r=boris"
merging dom/base/Document.cpp
merging dom/svg/SVGElement.cpp
merging modules/libpref/init/StaticPrefList.yaml
merging servo/components/style/properties/properties.mako.rs
warning: conflicts while merging dom/base/Document.cpp! (edit, then use 'hg resolve --mark')
warning: conflicts while merging dom/svg/SVGElement.cpp! (edit, then use 'hg resolve --mark')
abort: unresolved conflicts, can't continue
(use 'hg resolve' and 'hg graft --continue')

See https://bugzilla.mozilla.org/show_bug.cgi?id=1578661#c55

https://hg.mozilla.org/releases/mozilla-beta/rev/4bb822c2a23a