Something in this range: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=8883360b1edb&tochange=5811efc11011 Caused failures of form: https://tbpl.mozilla.org/php/getParsedLog.php?id=37570159&tree=Mozilla-Central https://tbpl.mozilla.org/php/getParsedLog.php?id=37570604&tree=Mozilla-Central { TEST-UNEXPECTED-FAIL | chrome://mochitests/content/browser/toolkit/mozapps/extensions/test/browser/browser_experiments.js | Experiment tab hidden by default. - false == true - JS frame :: chrome://mochitests/content/browser/toolkit/mozapps/extensions/test/browser/browser_experiments.js :: testInitialState :: line 48 TEST-UNEXPECTED-FAIL | chrome://mochitests/content/browser/toolkit/mozapps/extensions/test/browser/browser_select_selection.js | Should only be listing extensions - Got experiment, expected extension TEST-UNEXPECTED-FAIL | chrome://mochitests/content/browser/toolkit/mozapps/extensions/test/browser/test-window/browser_experiments.js | Experiment tab hidden by default. - false == true - JS frame :: chrome://mochitests/content/browser/toolkit/mozapps/extensions/test/browser/test-window/browser_experiments.js :: testInitialState :: line 48 } ...on nightly only mochitest-browser chrome runs (note the nightly test job appears on the pgo line due to bug 832050). Guessing that this is another case of bug 932211 rearing its delightful head.

That range includes: https://hg.mozilla.org/mozilla-central/rev/0e9ff2ea5085 https://hg.mozilla.org/mozilla-central/rev/7ade80b09c73 https://hg.mozilla.org/mozilla-central/rev/d7cbb56f75e1

I would guess that this has something to do with telemetry being off-by-default for on-checkin builds but on for nightlies.

If this is blocking anything in release land, it's OK to disable the test. I'm actively working on this test and the code behind it and I will address the problem before this feature is enabled for the Nightly audience.

I believe this will be fixed by bug 997188