The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/portage-stable/+/a6391cd50884318e45d87331b51349c938cdb2a5

commit a6391cd50884318e45d87331b51349c938cdb2a5
Author: Paul Moy <pmoy@chromium.org>
Date: Fri Sep 14 01:58:54 2018

which: upgraded package to upstream

Upgraded sys-apps/which to version 2.21 on amd64, arm, x86

BUG= chromium:882465 
TEST=Ran which -v, which which and verified results on grunt, kevin and
santa boards.

Change-Id: I865f7fbf1e67b7050e8d35463ad7fb94ba993387
Reviewed-on: https://chromium-review.googlesource.com/1216844
Commit-Ready: Paul Moy <pmoy@chromium.org>
Tested-by: Paul Moy <pmoy@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[modify] https://crrev.com/a6391cd50884318e45d87331b51349c938cdb2a5/sys-apps/which/metadata.xml
[add] https://crrev.com/a6391cd50884318e45d87331b51349c938cdb2a5/sys-apps/which/which-2.21.ebuild
[rename] https://crrev.com/a6391cd50884318e45d87331b51349c938cdb2a5/metadata/md5-cache/sys-apps/which-2.21
[modify] https://crrev.com/a6391cd50884318e45d87331b51349c938cdb2a5/sys-apps/which/Manifest
[delete] https://crrev.com/26bbc1f1c508b31c3dfb959886ce180e0e21ca48/sys-apps/which/which-2.20-r1.ebuild