The screens are never shown for now outside of tests.

Also rename the `error_timeout` illustration to just `error`, as it is
now used for all kinds of errors, not just timeouts.

Bug: 847985, 849323
Change-Id: Ieb73254c20948c5cdffb7513249cbae61980e1a2
TBR: dschuyler@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/1185008Reviewed-by: Jun Choi <hongjunchoi@chromium.org>
Commit-Queue: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585434}