GitLab

Adds offline scenario to Crostini configuration dialog. If Crostini
configuration failed while internet connection was missing dialog
informs user that Chromebook is offline and user can retry configuration
by hitting retry button.

Bug: 1029809
Change-Id: I6a5e006b5acb7300568eb6a40d9636725c229a12
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1947655Reviewed-by: Nic Hollingum <hollingum@google.com>
Commit-Queue: Olya Kalitova <okalitova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721487}