Currently Chromium OS installs adb using the upstream gentoo android-tools-5.1.1 ebuild, which pulls an ancient (circa 2013-09) version of android tools source code from:
https://projects.archlinux.org/svntogit/community.git/snapshot/community-caa300cf262afcf5bdb4dcc923dee54e3715fd5c.tar.gz

Updating portage-stable to android-tools-6.0.1_p79 brings in a ruby dependency which has a set of other dependencies (ragel,colm) that don't build for various (cross-compile?) reasons.

However, even the latest gentoo android-tools is the old (~2016-09).

The canonical source of this repository is:
https://android.googlesource.com/platform/system/core/+/master/adb

Among other things, it was moved from openssl to boringssl (2016-03) in the android-n-preview-3 branch:
  097b6bbc7 Switch fs_mgr and adb to libcrypto_utils.

Ideally we would change the ebuild to pull source from android.googlesource.com, and use a much newer release that uses boringssl rather than openssl.

Assigning to mnissler to find another an owner on the ARC++ team to upgrade this package.