Remove more chrome/browser deps

Removing chrome/browser deps from c/b/chromeos/settings code that, so
that the code can eventually be moved to src/chromeos/settings:

- Delete some chrome/browser includes that are now completely unused in
chrome/browser/chromeos/settings.

- Change SystemSettingsProvider to use UserManager, instead of
ProfileManager and LoginState, since UserManager does not depend on
chrome/browser

Bug: 446937
Change-Id: I5d1edb34643d6c48a8b8351af68ec9ae5c0118b4
Reviewed-on: https://chromium-review.googlesource.com/1238450
Commit-Queue: A Olsen <olsen@chromium.org>
Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594330}
4 files changed