The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/14192230400ba9aea176dc23e61bf933175d9f9a

commit 14192230400ba9aea176dc23e61bf933175d9f9a
Author: Kush Sinha <sinhak@chromium.org>
Date: Fri Dec 15 00:15:55 2017

Add policy for enforcing sign-in consistency between content area and OS

unit_tests --gtest_filter="SecondaryGoogleAccountSigninPolicyHandlerTest*"
and components_unittests --gtest_filter="SigninHeaderHelperTest*". In addition to these,
manual testing on Public Sessions, Guest Sessions and Multi-Sign in mode.

Bug:  784760 
Change-Id: I037cbcde5cd776b1b5a57b4788ea6fe3fd27ad74
Test: browser_tests --gtest_filter="PolicyPrefsTest.PolicyToPrefsMapping*",
Reviewed-on: https://chromium-review.googlesource.com/797590
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Reviewed-by: Pavol Marko <pmarko@chromium.org>
Commit-Queue: Kush Sinha <sinhak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524251}
[modify] https://crrev.com/14192230400ba9aea176dc23e61bf933175d9f9a/chrome/browser/chromeos/BUILD.gn
[add] https://crrev.com/14192230400ba9aea176dc23e61bf933175d9f9a/chrome/browser/chromeos/policy/secondary_google_account_signin_policy_handler.cc
[add] https://crrev.com/14192230400ba9aea176dc23e61bf933175d9f9a/chrome/browser/chromeos/policy/secondary_google_account_signin_policy_handler.h
[add] https://crrev.com/14192230400ba9aea176dc23e61bf933175d9f9a/chrome/browser/chromeos/policy/secondary_google_account_signin_policy_handler_unittest.cc
[modify] https://crrev.com/14192230400ba9aea176dc23e61bf933175d9f9a/chrome/browser/policy/configuration_policy_handler_list_factory.cc
[modify] https://crrev.com/14192230400ba9aea176dc23e61bf933175d9f9a/chrome/test/data/policy/policy_test_cases.json
[modify] https://crrev.com/14192230400ba9aea176dc23e61bf933175d9f9a/components/policy/resources/policy_templates.json
[modify] https://crrev.com/14192230400ba9aea176dc23e61bf933175d9f9a/components/signin/core/browser/chrome_connected_header_helper.cc
[modify] https://crrev.com/14192230400ba9aea176dc23e61bf933175d9f9a/components/signin/core/browser/signin_header_helper_unittest.cc
[modify] https://crrev.com/14192230400ba9aea176dc23e61bf933175d9f9a/tools/metrics/histograms/enums.xml

With the SecondaryGoogleAccountSigninAllowed enabled inside YAPS, the user was able to sign in with another google account. No new policies were imported. While  SecondaryGoogleAccountSigninAllowed was set to false, end user was not able to sign in to another google account while logged in using primary account.

Tested on Sumo Device 
Dev M66 Chrome OS 10406.0.0, 66.0.3344.0

"Tested on Sumo Device 
Dev M66 Chrome OS 10406.0.0, 66.0.3344.0"

vaandres@ : The test target is M65 (currently in beta), not Dev M66. Can you check it on M65 please?

Verified on Sumo M65 10323.38.0 65.0.3325.85

Feature is functioning properly

Thanks for re-checking it!

I'm looking for the SecondaryGoogleAccountSigninAllowed in my GAFE Admin console and I can't find it. Am I looking in the right place?

Probably. I don't think it's released yet.

/Kim

SecondaryGoogleAccountSignInAllowed has not been exposed in the admin console yet.

@vaandres@chromium.org do we have an idea of when it might be exposed to the admin console?

Please check https://bugs.chromium.org/p/chromium/issues/detail?id=547933#c82 :

"If you'd like to test this feature, please sign up here for early access: https://goo.gl/AXR2hV"