GitLab

ConcurrentHashMap has a bug on L.
Also adds a checkstyle check to prevent future uses.

Bug: 905903
Change-Id: Ic6afed17b5d7d3c6a150935117fb33e0408955e4
Reviewed-on: https://chromium-review.googlesource.com/c/1407493Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Commit-Queue: agrieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622143}