GitLab

Because writing out
std::vector<printing::PrinterSemanticCapsAndDefaults::Paper> takes up
the entire line. Also initialize more class members in print_backend.h.

Change-Id: Ia623501c2d124ef3c6a601cb863585d3e8772776
Reviewed-on: https://chromium-review.googlesource.com/c/1357620Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613338}