Can add GetAuthError() equivalent at the same time as they're related.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b61bd93da1ad238f66d1ed9fd769fc6a601a69c4

commit b61bd93da1ad238f66d1ed9fd769fc6a601a69c4
Author: Colin Blundell <blundell@chromium.org>
Date: Mon Oct 08 14:02:55 2018

Allow FakeO2TSDelegate::UpdateAuthError() to take in transient errors

This CL extends FakeO2TSDelegate to support taking in transient errors
and dropping them; before, it would just update the auth error, which
violates the contract of O2TS::GetAuthError() and results in a DCHECK
failing inside that class.

This better reflects production behavior (e.g., of MutablePO2TSDelegate)
and allows an upcoming CL to test proper behavior in the event of a
transient error occurring.

Bug:  882861 
Change-Id: Icbf2020b1b7fd9a0992e0b17fd74fc9b3f0eaf42
Reviewed-on: https://chromium-review.googlesource.com/c/1268017
Reviewed-by: David Roger <droger@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597553}
[modify] https://crrev.com/b61bd93da1ad238f66d1ed9fd769fc6a601a69c4/google_apis/gaia/fake_oauth2_token_service_delegate.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a62fc12d315d648d4e619e38fd95351159902ada

commit a62fc12d315d648d4e619e38fd95351159902ada
Author: Colin Blundell <blundell@chromium.org>
Date: Mon Oct 08 14:40:36 2018

IdentityManager: Add APIs for querying refresh token error state

Will be needed by multiple clients for converting away from
ProfileOAuth2TokenService.

Bug:  882861 
Change-Id: Ie648a701a02d34e786703604cb8d1f7f080202bc
Reviewed-on: https://chromium-review.googlesource.com/c/1267499
Reviewed-by: David Roger <droger@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597558}
[modify] https://crrev.com/a62fc12d315d648d4e619e38fd95351159902ada/services/identity/public/cpp/identity_manager.cc
[modify] https://crrev.com/a62fc12d315d648d4e619e38fd95351159902ada/services/identity/public/cpp/identity_manager.h
[modify] https://crrev.com/a62fc12d315d648d4e619e38fd95351159902ada/services/identity/public/cpp/identity_manager_unittest.cc