GitLab

- Make AuthSyncObserver observe SigninErrorController in addition
  to sync service so that auth errors caused by other services
  are caught as well.
- Fix an edge case that OAuth2LoginManager marks valid oauth2
  token when it thinks /MergeSession succeeds regardless of
  whether there is any auth error;

Bug: 760610
Test: OAuth2Test.SetInvalidTokenStatus

Change-Id: Idbaee9f7faa1aa2aff939a1540bfcfdd9f49c96c
Reviewed-on: https://chromium-review.googlesource.com/658378
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Cr-Commit-Position: refs/heads/master@{#504391}