GitLab

When during demo mode setup error occurs the message displayed to the
user contains description of the problem and suggested recovery method.
It helps users as well as support and developers.

Bug: 889604
Test: demo setup unit and browser tests.
Change-Id: Ia2ea4b1d9e1b4667ca9dde139d3a4aaba3a58cd0
Reviewed-on: https://chromium-review.googlesource.com/c/1280311Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Reviewed-by: Rahul Chaturvedi <rkc@chromium.org>
Commit-Queue: Aga Wronska <agawronska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602425}