It was added in b0b60641b8 as part of the fix for an infinite loop.

Sergio, can you expand on c#2? Thanks!

Colin, I think he wanted to give some context from where the dependency came from.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8a3b374352516c834b2fb7e7389d2caef2200083

commit 8a3b374352516c834b2fb7e7389d2caef2200083
Author: Henrique Ferreiro <hferreiro@igalia.com>
Date: Fri Jan 18 12:56:28 2019

Clean unused code from login_service_ui_factory.cc

LoginUIService stoped using SigninManagerFactory and
ProfileOAuth2TokenServiceFactory in https://crrev.com/c/1349691, so remove the
dependencies on those factories. UnifiedConsentServiceFactory and
ProfileSyncServiceFactory dependencies are kept because there are runtime
dependencies between those services. Also, remove unused includes.


Bug:  920242 
Change-Id: I13c29cde2c7870ce6be09b5f1172e8ab51753195
Reviewed-on: https://chromium-review.googlesource.com/c/1414930
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Commit-Queue: Mihai Sardarescu <msarda@chromium.org>
Auto-Submit: Henrique Ferreiro <hferreiro@igalia.com>
Cr-Commit-Position: refs/heads/master@{#624091}
[modify] https://crrev.com/8a3b374352516c834b2fb7e7389d2caef2200083/chrome/browser/ui/webui/signin/login_ui_service_factory.cc