Mark more members const in cloud_print::JobStatusUpdater.

Also remove some unused/redundant headers, and remove a check that will
always evaluate to true.

Change-Id: I816ab3154c50b1f0f1f8c4fc738760b97e607d7e
Reviewed-on: https://chromium-review.googlesource.com/c/1277677
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599057}
2 files changed