We should be able to use the same RemoteSetting instance for all the URL Classifier features. Besides that, we should also avoid syncing remote setting data for every features (See Bug 1617971 Comment 4)

https://hg.mozilla.org/mozilla-central/rev/cffc27728f9e
https://hg.mozilla.org/mozilla-central/rev/0dc7fbadfe15

This is getting backed out for causing bug 1627377. This is because I missed the fact that not all features get created immediately when the service initializes, and when features get created later, they get no initial data and so never properly initialize. I'll put up a combined patch that addresses this and request review.

Backed out for causing Bug 1627377.

Push with failures: https://treeherder.mozilla.org/#/jobs?repo=autoland&selectedJob=296207604&group_state=expanded&searchStr=windows%2C10%2Cx64%2Cshippable%2Copt%2Cmochitests%2Ctest-windows10-64-shippable%2Fopt-mochitest-browser-chrome-e10s-7%2Cm%28bc7%29&tochange=cffc27728f9edce1393f3a0c1ec06e18d82b5ace&fromchange=449fd8a4035ec5f19127f2d042c6ee6d7b6bf740

Failure log: https://treeherder.mozilla.org/logviewer.html#?job_id=296192718&repo=autoland

Backout link: https://hg.mozilla.org/integration/autoland/rev/890c9bc949ba110737e6d15804fb282705972f8e

[task 2020-04-04T11:43:38.176Z] 11:43:38 INFO - TEST-PASS | toolkit/components/antitracking/test/browser/browser_siteSpecificWorkArounds.js | callbackAfterRemoval must be passed when accessRemoval is non-null -
[task 2020-04-04T11:43:38.176Z] 11:43:38 INFO - Waiting for the skip list service to initialize...
[task 2020-04-04T11:43:38.176Z] 11:43:38 INFO - Buffered messages finished
[task 2020-04-04T11:43:38.176Z] 11:43:38 INFO - TEST-UNEXPECTED-FAIL | toolkit/components/antitracking/test/browser/browser_siteSpecificWorkArounds.js | Uncaught exception - Skip list service initialized - timed out after 50 tries.
[task 2020-04-04T11:43:38.176Z] 11:43:38 INFO - Leaving test bound
[task 2020-04-04T11:43:38.176Z] 11:43:38 INFO - Entering test bound
[task 2020-04-04T11:43:38.176Z] 11:43:38 INFO - Cleaning up.
[task 2020-04-04T11:43:38.317Z] 11:43:38 INFO - Leaving test bound
[task 2020-04-04T11:43:38.318Z] 11:43:38 INFO - Entering test bound
[task 2020-04-04T11:43:38.319Z] 11:43:38 INFO - Starting non-blocking cookieBehavior (0) without allow list test localStorage with a tracker that is whitelisted via a pref running in a normal window with iframe sandbox set to null and access removal set to null
[task 2020-04-04T11:43:38.319Z] 11:43:38 INFO - TEST-PASS | toolkit/components/antitracking/test/browser/browser_siteSpecificWorkArounds.js | callbackAfterRemoval must be passed when accessRemoval is non-null -
[task 2020-04-04T11:43:38.359Z] 11:43:38 INFO - Waiting for the skip list service to initialize...
[task 2020-04-04T11:43:43.479Z] 11:43:43 INFO - Not taking screenshot here: see the one that was previously logged

Backout merged: https://hg.mozilla.org/mozilla-central/rev/890c9bc949ba

hi gijs,
Thank you for your help and sorry for not thinking and testing carefully while working on this.
I didn't realize that you already have a patch reviewed while working on my fix yesterday.
I wrote testcases anyway, maybe we can still use that part.

https://hg.mozilla.org/mozilla-central/rev/465fa77baabe