The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8876ba875ac9a5d4676b75dad1aa97e562839f01

commit 8876ba875ac9a5d4676b75dad1aa97e562839f01
Author: Jacob Dufault <jdufault@google.com>
Date: Tue Mar 27 22:55:43 2018

cros: Crash on lock if we enter bad authentication state.

There are numerous user reports of this issue. If we start crashing
in this situation I think there will be more useful diagnostics. The
only known way to get out of this state is to logout, so this is not a
UX regression.

Bug:  820671 
Change-Id: Ie3643e9c841fdd5acaa65a2d0838da5f46c822a8
Reviewed-on: https://chromium-review.googlesource.com/974508
Commit-Queue: Jacob Dufault <jdufault@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546304}
[modify] https://crrev.com/8876ba875ac9a5d4676b75dad1aa97e562839f01/ash/login/login_screen_controller.cc
[modify] https://crrev.com/8876ba875ac9a5d4676b75dad1aa97e562839f01/ash/login/login_screen_controller.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c06d6ca5d4f5f3e102e50c1f19f5969b85e0ea75

commit c06d6ca5d4f5f3e102e50c1f19f5969b85e0ea75
Author: Jacob Dufault <jdufault@google.com>
Date: Tue Apr 24 23:49:17 2018

cros: Log authentication stage in LoginScreenController::OnShow.

There was one crash report in this method, but the crash did not seem to include
local variables. Log the value of authentication_stage_ to capture it.

Bug:  820671 
Change-Id: I82c25b8a58f0993a9eef94c497c2c3e06c48b255
Reviewed-on: https://chromium-review.googlesource.com/1015880
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Jacob Dufault <jdufault@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553372}
[modify] https://crrev.com/c06d6ca5d4f5f3e102e50c1f19f5969b85e0ea75/ash/login/login_screen_controller.cc
[modify] https://crrev.com/c06d6ca5d4f5f3e102e50c1f19f5969b85e0ea75/ash/login/login_screen_controller.h
[modify] https://crrev.com/c06d6ca5d4f5f3e102e50c1f19f5969b85e0ea75/ash/login/ui/lock_screen.cc

Jacob, we haven't had reports of this in a long time, I'm going to close. Feel free to reopen as needed.