Add update cohort name during Chrome update as an enum histogram

Bug: 943641

Change-Id: I4580b76970567b99cc942a2b27c26facd44c675f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1501757
Commit-Queue: Nik Bhagat <nikunjb@google.com>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Joshua Pawlicki <waffles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#643153}
2 files changed