This is being addressed as part of the CL 1290931

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/16b57289a75cdf261f5aaea4bd5b3dacc4bbab96

commit 16b57289a75cdf261f5aaea4bd5b3dacc4bbab96
Author: Mario Sanchez Prada <mario@igalia.com>
Date: Tue Oct 23 17:45:56 2018

Convert UserPolicySigninService[Base] to IdentityManager::Observer

This patch converts both classes at the same time due to the
interdependencies (e.g. signin_manager() helper) that would make
it harder to do it separately.

TBR=msarda@chromium.org

Bug:  887449 ,  887450 ,  890783 ,  890782 ,  890782 
Change-Id: Ia5d2834e449c7da635445e0baea2910b23903596
Reviewed-on: https://chromium-review.googlesource.com/c/1290931
Commit-Queue: Mario Sanchez Prada <mario@igalia.com>
Reviewed-by: Sergey Poromov <poromov@chromium.org>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602005}
[modify] https://crrev.com/16b57289a75cdf261f5aaea4bd5b3dacc4bbab96/chrome/browser/policy/cloud/user_policy_signin_service.cc
[modify] https://crrev.com/16b57289a75cdf261f5aaea4bd5b3dacc4bbab96/chrome/browser/policy/cloud/user_policy_signin_service.h
[modify] https://crrev.com/16b57289a75cdf261f5aaea4bd5b3dacc4bbab96/chrome/browser/policy/cloud/user_policy_signin_service_base.cc
[modify] https://crrev.com/16b57289a75cdf261f5aaea4bd5b3dacc4bbab96/chrome/browser/policy/cloud/user_policy_signin_service_base.h
[modify] https://crrev.com/16b57289a75cdf261f5aaea4bd5b3dacc4bbab96/chrome/browser/policy/cloud/user_policy_signin_service_factory.cc
[modify] https://crrev.com/16b57289a75cdf261f5aaea4bd5b3dacc4bbab96/chrome/browser/policy/cloud/user_policy_signin_service_mobile.cc
[modify] https://crrev.com/16b57289a75cdf261f5aaea4bd5b3dacc4bbab96/chrome/browser/policy/cloud/user_policy_signin_service_mobile.h
[modify] https://crrev.com/16b57289a75cdf261f5aaea4bd5b3dacc4bbab96/chrome/browser/policy/cloud/user_policy_signin_service_unittest.cc
[modify] https://crrev.com/16b57289a75cdf261f5aaea4bd5b3dacc4bbab96/chrome/browser/ui/webui/signin/dice_turn_sync_on_helper_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/731a1cf7d041892553877dde4bee81bf0ae83a61

commit 731a1cf7d041892553877dde4bee81bf0ae83a61
Author: Antonio Gomes <tonikitoo@igalia.com>
Date: Thu Nov 08 13:06:56 2018

[s13n] Convert UserPolicySigninServiceTest way from SigninManager

This makes use of the helper IdentityTestEnvironmentProfileAdaptor.
In order to be able to construct the Profile object the same way as the
test originally was, and additional optional parameter was added to
IdentityTestEnvironmentProfileAdaptor::CreateProfileForIdentityTestEnvironment.

BUG= 890783 

Change-Id: I5c2a48dd4aa7e7377f8a7806717b513b7f27bfe0
Reviewed-on: https://chromium-review.googlesource.com/c/1301814
Reviewed-by: Colin Blundell <blundell@chromium.org>
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Cr-Commit-Position: refs/heads/master@{#606434}
[modify] https://crrev.com/731a1cf7d041892553877dde4bee81bf0ae83a61/chrome/browser/policy/cloud/user_policy_signin_service_unittest.cc
[modify] https://crrev.com/731a1cf7d041892553877dde4bee81bf0ae83a61/chrome/browser/signin/identity_test_environment_profile_adaptor.cc
[modify] https://crrev.com/731a1cf7d041892553877dde4bee81bf0ae83a61/chrome/browser/signin/identity_test_environment_profile_adaptor.h