As part of the Search Configuration, we'd like to be able to roll out different configurations as part of experiments.

To manage this, we will:

• Re-use the existing browser.search.cohort preference. This will normally be set/reset by an experiment tool, e.g. normandy or some other prefs-setting experimentation tool.
• In the configuration, we will have a new option in the application section for cohort. The application section appears with appliesTo sections.
  • If no cohort value is set, the appliesTo section applies everywhere.
  • If the cohort value is set, and it is a different value to the preference, or if the preference is not set, then the section will not apply.
  • If the cohort value is set, and the preference matches, then the section will apply.

Backed out changeset 53f941b09ee9 (bug 1572030) for xpcshell failures at toolkit/components/search/tests/xpcshell/test_engine_selector.js

Backout: https://hg.mozilla.org/integration/autoland/rev/db8bb69c4e664be524154efc2f7f82c2e49dbded

Failure push: https://treeherder.mozilla.org/#/jobs?repo=autoland&revision=53f941b09ee9c3bc7cf42a56a63f44224591634b

Failure log: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=265919990&repo=autoland&lineNumber=4794

task 2019-09-10T13:50:27.390Z] 13:50:27 INFO - TEST-START | toolkit/components/search/tests/xpcshell/test_engine_selector.js
[task 2019-09-10T13:50:27.893Z] 13:50:27 WARNING - TEST-UNEXPECTED-FAIL | toolkit/components/search/tests/xpcshell/test_engine_selector.js | xpcshell return code: 0
[task 2019-09-10T13:50:27.893Z] 13:50:27 INFO - TEST-INFO took 506ms
[task 2019-09-10T13:50:27.893Z] 13:50:27 INFO - >>>>>>>
[task 2019-09-10T13:50:27.893Z] 13:50:27 INFO - PID 5249 | [5249, Main Thread] WARNING: Couldn't get the user appdata directory. Crash events may not be produced.: file /builds/worker/workspace/build/src/toolkit/crashreporter/nsExceptionHandler.cpp, line 2632
[task 2019-09-10T13:50:27.895Z] 13:50:27 INFO - PID 5249 | [5249, Main Thread] WARNING: NS_ENSURE_SUCCESS(rv, kKnownEsrVersion) failed with result 0x80004002: file /builds/worker/workspace/build/src/toolkit/components/resistfingerprinting/nsRFPService.cpp, line 661
[task 2019-09-10T13:50:27.896Z] 13:50:27 INFO - PID 5249 | [5249, Main Thread] WARNING: NS_ENSURE_SUCCESS(rv, rv) failed with result 0x80520012: file /builds/worker/workspace/build/src/extensions/permissions/nsPermissionManager.cpp, line 2883
[task 2019-09-10T13:50:27.896Z] 13:50:27 INFO - (xpcshell/head.js) | test MAIN run_test pending (1)
[task 2019-09-10T13:50:27.896Z] 13:50:27 INFO - (xpcshell/head.js) | test run_next_test 0 pending (2)
[task 2019-09-10T13:50:27.896Z] 13:50:27 INFO - (xpcshell/head.js) | test MAIN run_test finished (2)
[task 2019-09-10T13:50:27.896Z] 13:50:27 INFO - running event loop
[task 2019-09-10T13:50:27.896Z] 13:50:27 INFO - toolkit/components/search/tests/xpcshell/test_engine_selector.js | Starting
[task 2019-09-10T13:50:27.896Z] 13:50:27 INFO - (xpcshell/head.js) | test pending (2)
[task 2019-09-10T13:50:27.896Z] 13:50:27 INFO - (xpcshell/head.js) | test run_next_test 0 finished (2)
[task 2019-09-10T13:50:27.896Z] 13:50:27 INFO - PID 5249 | *** Search: SearchEngineSelector fetchEngineConfiguration us:en-US
[task 2019-09-10T13:50:27.900Z] 13:50:27 INFO - PID 5249 | JavaScript strict warning: resource://gre/modules/SearchEngineSelector.jsm, line 87: ReferenceError: reference to undefined property "webExtensionLocale"
[task 2019-09-10T13:50:27.900Z] 13:50:27 INFO - PID 5249 | *** Search: SearchEngineSelector fetchEngineConfiguration: {"engines":[{"engineName":"lycos","orderHint":1000,"default":"yes"},{"engineName":"altavista","orderHint":2000,"defaultPrivate":"yes"},{"engineName":"aol","orderHint":500,"webExtensionLocale":"en-US"}],"privateDefault":"altavista"}
[

I bet that's because I landed bug 1572488 on autoland earlier today (before your patch)

Yeh I had done a try run this morning to make sure :) will rebase once that hits m-c and fix / reland

Backed out for ES Lint failure.

Push with failure: https://treeherder.mozilla.org/#/jobs?repo=autoland&revision=dfd2dc592f0f773f2331e79289be6801917a3d41&searchStr=Linting%2Copt%2CJavaScript%2Cchecks%2Csource-test-mozlint-eslint%2Cjs%28ES%29&selectedJob=265987789

Failure log: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=265987789&repo=autoland&lineNumber=76

TEST-UNEXPECTED-ERROR | /builds/worker/checkouts/gecko/toolkit/components/search/tests/xpcshell/test_engine_selector.js:111:14 | Replace "altavista","aol", with ?"altavista",?"aol",? (prettier/prettier)

Backout: https://hg.mozilla.org/integration/autoland/rev/25d6ae32aa62c7fff8b6d43a9147b696b197d1dd

This reverts commit 6e8f8684501061d1d759d1dab40b867e90f2b85d.

Ugh very sorry, this change seems to have got caught out a few times, but all looking green now and relanded

https://hg.mozilla.org/mozilla-central/rev/ba563f823a56