While testing it, I was able to hit that DCHECK [1] But this is not a crasher.

To leave the managed account, an alert dialog is created [2]. And in the callback, the delegate is called first [3], and then the dialog is cleanup in the following line (setting _alertCoordinator to nil).
The issue is the delegate calls -[AuthenticationFlowPerformer showManagedConfirmationForHostedDomain:viewController:] which creates a new alert dialog and stores it in _alertCoordinator, and this is done before the cleanup of the first alert dialog. So DCHECK [1] fails.

The consequence is _alertCoordinator is set to nil while the dialog box is opened. This should not be a crasher since the alert is being displayed.
This issue happens for all alert dialog in that file.

[1] https://cs.chromium.org/chromium/src/ios/chrome/browser/ui/authentication/authentication_flow_performer.mm?l=321
[2] https://cs.chromium.org/chromium/src/ios/chrome/browser/ui/authentication/authentication_flow_performer.mm?l=205
[3] https://cs.chromium.org/chromium/src/ios/chrome/browser/ui/authentication/authentication_flow_performer.mm?l=216

If the original crash is only related from switching to a managed account to another managed account. This bug should happens very rarely. It is rare to have one manage account, even more to have 2, and really rare to switch from one sync account to another.

I missed that test:
https://cs.chromium.org/chromium/src/ios/chrome/browser/ui/authentication/authentication_flow_performer.mm?l=387

So as far as I know there is no consequence about that failing DCHECK.

@treib Do you know what could happen? I can't find any crash on the UI code. Could it be in the sync code?

I can't reproduce that crash.

@noyau, what was the chrome version?

Thanks,

First, what exactly does "managed account" mean here? Dasher account with enterprise policies?

Second, what makes you think this could be related to Sync? I can't rule it out obviously; without a stack trace or something, there's really no way to tell.

First:
For @noyau, it was from @google.com account to his personal domain name account.

Second:
I have no more information on that bug. But to change sync account, I turn off sync and then turn on sync. So I'm wondering if you could know any crasher that could help to understand that issue.

But the problem here is I have no log, no crash log, and nobody can reproduce it...

I created  crbug.com/890332  to track #c1 since this issue is not a crash, therefore it is not the issue that @noyau experienced.

Chrome version: 70.0.3538.32 beta

Let me know if you can reproduce this bug.

noyau@: triage ping. Can this be closed? Thx.

Triage ping: are you still able to repoduce the bug? Or it can be closed?

Triage ping for noyau@, thanks!

I can't repro anymore.

Closing this since it's not actionable at this point. Thanks for reporting!