login: Abstract out the interface to crossystem.
This is required for SessionManagerImpl::UpdateSystemSettings() unit
tests which will be added in a separate CL.
BUG=chrome-os-partner:50142
TEST=verified that block_devmode is still updated on policy changes
Change-Id: I11fe94b14d6e1bf9d98d8e0920fea48c0c12588f
Reviewed-on: https://chromium-review.googlesource.com/328993
Commit-Ready: Thiemo Nagel <tnagel@chromium.org>
Tested-by: Thiemo Nagel <tnagel@chromium.org>
Reviewed-by: Thiemo Nagel <tnagel@chromium.org>
14 files changed
