SystemSettingsProvider dep back to LoginState

SystemSettingProvider had a dep on both LoginState and ProfileManager,
in order to check if the user had permission to change the timezone.
ProfileManager is in chrome/browser and I am trying to remove
chrome/browser deps, so I changed the code to use only UserManager.
See https://chromium-review.googlesource.com/1238450

I realized afterwards that UserManager deps are also currently not
allowed in src/chromeos, where this code will soon live. Rather than
expand the list of deps (which should be kept small), I have updated
LoginState so that only it is needed here (instead of ProfileManager or
UserManager). So, the last change is no longer needed, and is reverted.

I also tidied up conversion code in ChromeUserManager slightly -
Moving if-else-else chain into a helper function with switch + return
means that the compiler checks that all cases are handled.

Bug: 446937
Change-Id: I3aa44cacdef752f997d12b647d6e073f806371d3
Reviewed-on: https://chromium-review.googlesource.com/1249209
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: A Olsen <olsen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595777}
5 files changed