The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d5e3ad6f79781cf00cc24447d70772cd31cd88bf

commit d5e3ad6f79781cf00cc24447d70772cd31cd88bf
Author: Roman Sorokin <rsorokin@chromium.org>
Date: Tue Jul 10 14:31:40 2018

[UMA] Chromad: Add histogram to track streamline domain join

This CL adds histogram "Enterprise.ActiveDirectoryJoin" to track
the way device is joined to the Active Directory domain.

BUG= chromium:855615 
TEST=manual

Change-Id: Idc63ec1ab2d6faf0ed4203db0fc8835c357ef19e
Reviewed-on: https://chromium-review.googlesource.com/1120168
Commit-Queue: Roman Sorokin <rsorokin@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Jacob Dufault <jdufault@chromium.org>
Reviewed-by: Lutz Justen <ljusten@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573715}
[modify] https://crrev.com/d5e3ad6f79781cf00cc24447d70772cd31cd88bf/chrome/browser/ui/webui/chromeos/login/enrollment_screen_handler.cc
[modify] https://crrev.com/d5e3ad6f79781cf00cc24447d70772cd31cd88bf/chrome/browser/ui/webui/chromeos/login/enrollment_screen_handler.h
[modify] https://crrev.com/d5e3ad6f79781cf00cc24447d70772cd31cd88bf/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/d5e3ad6f79781cf00cc24447d70772cd31cd88bf/tools/metrics/histograms/histograms.xml

Enterprise.ActiveDirectoryJoin has nonzero count (still quite low, but that's as expected)