GitLab

Required by the standard, and, apparently, MSVC2017.

Also remove redundant `inline`s (methods defined within a class body
are implicit inilne already), and use the iterator typedefs more.

BUG=none

Review-Url: https://codereview.chromium.org/2570343002
Cr-Commit-Position: refs/heads/master@{#438557}