GitLab

This change moves base::Contains into a new base/containers/contains.h
header. This organizes base/stl_util.h a bit, which has become somewhat
of a dumping ground.

Bug: 970209
Change-Id: I7f0df1a1cbfb323f060f2b7a67bcf9c139aa589e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2578941Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#835094}