I'm fixing a bug where a bad user name would yield ERROR_PARSE_FAILED instead of ERROR_BAD_USER_NAME, but this doesn't help.

Does Chrome handle unknown errors or does it not show anything in this case?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/9279946775c17efee6588628ebd98995ee54cf53

commit 9279946775c17efee6588628ebd98995ee54cf53
Author: Lutz Justen <ljusten@chromium.org>
Date: Fri Apr 21 09:34:47 2017

authpolicy: Fix error code returned from entering bad user name

AuthenticateUser used to return ERROR_BAD_USER_NAME when the user
entered a wrong user name. After net ads search got moved before
kinit, that changed to ERROR_PARSE_FAILED because search returned
'Got 0 replies', which failed to parse the account info. This CL
returns ERROR_BAD_USER_NAME if 'Got 0 replies' is received.

BUG= chromium:712720 
TEST=Compiled, verified on device that the proper code is sent.

Change-Id: Ibc78a7582d8ffb0fba3e7153f716a5d2d6b3b0e0
Reviewed-on: https://chromium-review.googlesource.com/481261
Commit-Ready: Lutz Justen <ljusten@chromium.org>
Tested-by: Lutz Justen <ljusten@chromium.org>
Reviewed-by: Roman Sorokin <rsorokin@chromium.org>

[modify] https://crrev.com/9279946775c17efee6588628ebd98995ee54cf53/authpolicy/authpolicy_unittest.cc
[modify] https://crrev.com/9279946775c17efee6588628ebd98995ee54cf53/authpolicy/samba_interface.cc
[modify] https://crrev.com/9279946775c17efee6588628ebd98995ee54cf53/authpolicy/authpolicy_parser_main.cc

Can't reproduce.