GitLab

Use base::NoDestructor, range-based for loops, and initialize members in
headers. Also mark some constants as constexpr.

Change-Id: I7cfef2e80f8fc285af560f48cfbcaf264b03513e
Reviewed-on: https://chromium-review.googlesource.com/1189542Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586370}