The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9ef26f9fe4eb0d3818139423f485aebf005bb638

commit 9ef26f9fe4eb0d3818139423f485aebf005bb638
Author: khmel@google.com <khmel@google.com>
Date: Tue Jul 10 17:44:43 2018

arc: Add Arc.StateByUserType metric.

BUG= 855265 
TEST=Manually

Change-Id: I77cf19b06ffd76de3a5f8cfda36ee0ea0fd34d62
Reviewed-on: https://chromium-review.googlesource.com/1111114
Reviewed-by: Josh Horwich <jhorwich@chromium.org>
Reviewed-by: Elijah Taylor <elijahtaylor@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Yury Khmel <khmel@google.com>
Cr-Commit-Position: refs/heads/master@{#573799}
[modify] https://crrev.com/9ef26f9fe4eb0d3818139423f485aebf005bb638/chrome/browser/chromeos/arc/arc_optin_uma.cc
[modify] https://crrev.com/9ef26f9fe4eb0d3818139423f485aebf005bb638/chrome/browser/chromeos/arc/arc_optin_uma.h
[modify] https://crrev.com/9ef26f9fe4eb0d3818139423f485aebf005bb638/chrome/browser/chromeos/arc/arc_session_manager.cc
[modify] https://crrev.com/9ef26f9fe4eb0d3818139423f485aebf005bb638/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/9ef26f9fe4eb0d3818139423f485aebf005bb638/tools/metrics/histograms/histograms.xml