GitLab

Make sure color models are color, and B&W models are not. Since
PrintBackendCupsHelperTest has to deal with enum ColorModel anyway, it
is a convenient spot to also exercise IsColorModelSelected().

Bug: 1069315
Change-Id: Ie3f665d5245e5aee04010f7c61d7b193936a0655
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2143372
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Daniel Hosseinian <dhoss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757982}