central-as-beta simulation: https://treeherder.mozilla.org/#/jobs?repo=try&group_state=expanded&selectedTaskRun=fWktsz3nQ5y8bgpIEloAKw-0&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel%2Crunnable&revision=bdde24953684f564f9d63151e8af85149c1cc5f7

Failure logs (so far, push is still in progress):
https://treeherder.mozilla.org/logviewer.html#?job_id=302443078&repo=try
https://treeherder.mozilla.org/logviewer.html#?job_id=302443058&repo=try

Looking to the logs in the failures linked in comment 0, the failure should be related to the following error:

"CONSOLE_MESSAGE: (error) [JavaScript Error: "Cc['@mozilla.org/extensions/storage/sync;1'] is undefined" {file: "resource://gre/modules/ExtensionStorageSync.jsm" line: 32}]

and that should be because those components are currently built only in Nightly, see:

• https://searchfox.org/mozilla-central/rev/9193635dca8cfdcb68f114306194ffc860456044/toolkit/components/extensions/storage/components.conf#8,19
• https://searchfox.org/mozilla-central/rev/9193635dca8cfdcb68f114306194ffc860456044/toolkit/moz.configure#1986-1995

I'm not clearing the needinfo assigned to markh, so that he can double-check with Lina how to proceed to handle this before the merge to beta.

Bug 1638557 sounds related?

(In reply to Julien Cristau [:jcristau] from comment #2)

Bug 1638557 sounds related?

Yes, from a quick look to Lina's patch in Bug 1638557 the test failure tracked by this bug should also be fixed by it.

Verified fixed in today's central as beta simulation.