Adding another dependency

Hey Sergio! Can you expand on what the relationship between this bug and RendererUpdater is? Thanks!

taking this one as I migrated UserCloudPolicyTokenForwarder itself.

removing dep to  bug 887453  as it turns out to not be the case.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a26438966ef89a6c2a983032b2467bd7525949be

commit a26438966ef89a6c2a983032b2467bd7525949be
Author: Antonio Gomes <tonikitoo@igalia.com>
Date: Fri Nov 16 14:38:19 2018

[s13n] Convert user_cloud_policy_manager_chromeos_unittest.cc to IdentityManager

This CL removes the direct needs to SigninManager and PO2TS from
UserCloudPolicyManagerChromeOSTest code.

CL also removes left-over code from [1], namely kChildAccountId,
kChildTestGaiaId and ::AddAndSwitchToChildAccountWithProfile.

[1] https://crrev.com/c/1089462

BUG= 894075 , 904358 

Change-Id: Ibfddebed7747a2f3cf0a4e8cadf9a4b71d804e18
Reviewed-on: https://chromium-review.googlesource.com/c/1332748
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Cr-Commit-Position: refs/heads/master@{#608770}
[modify] https://crrev.com/a26438966ef89a6c2a983032b2467bd7525949be/chrome/browser/chromeos/policy/user_cloud_policy_manager_chromeos_unittest.cc
[modify] https://crrev.com/a26438966ef89a6c2a983032b2467bd7525949be/services/identity/public/cpp/identity_test_environment.cc
[modify] https://crrev.com/a26438966ef89a6c2a983032b2467bd7525949be/services/identity/public/cpp/identity_test_environment.h