MaybeUpgradeCrostini is called at login.

If there is an already installed cros-termina component, and that component
is not compatible, an attempt is made to dowload and install a new version.

If the user is offline at login, the install attempt may be made later.

Bug: 862199
Change-Id: I20b8790f1258dcfba8003f1031fdeb5c198d5095
Reviewed-on: https://chromium-review.googlesource.com/1139852
Reviewed-by: Timothy Loh <timloh@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Xiaochu Liu <xiaochu@chromium.org>
Commit-Queue: Nicholas Verne <nverne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576678}
8 files changed