Also, consider removing any staged but unsent logs when UKM gets disabled in this manner.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/477b5b9f1c8315c88d385838e160b9b73781ff18

commit 477b5b9f1c8315c88d385838e160b9b73781ff18
Author: Robert Kaplow <rkaplow@chromium.org>
Date: Fri Feb 02 17:46:51 2018

Test group policy for UKM.

Refactored the pref-setting logic out of metrics_reporting_state_browsertest in a way it could be reused in UKM. Setup a parametrized UKM test which tests the enabled/disabled group policy state based on prefs and verified service is enabled/disabled.

Bug:  805983 
Change-Id: Ic303e4116826990e7780125f186b0028a8fd6a5e
Reviewed-on: https://chromium-review.googlesource.com/895390
Commit-Queue: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534086}
[modify] https://crrev.com/477b5b9f1c8315c88d385838e160b9b73781ff18/chrome/browser/BUILD.gn
[modify] https://crrev.com/477b5b9f1c8315c88d385838e160b9b73781ff18/chrome/browser/metrics/chrome_metrics_service_accessor.h
[modify] https://crrev.com/477b5b9f1c8315c88d385838e160b9b73781ff18/chrome/browser/metrics/metrics_reporting_state_browsertest.cc
[add] https://crrev.com/477b5b9f1c8315c88d385838e160b9b73781ff18/chrome/browser/metrics/testing/metrics_reporting_pref_helper.cc
[add] https://crrev.com/477b5b9f1c8315c88d385838e160b9b73781ff18/chrome/browser/metrics/testing/metrics_reporting_pref_helper.h
[modify] https://crrev.com/477b5b9f1c8315c88d385838e160b9b73781ff18/chrome/browser/metrics/ukm_browsertest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/076f8e1b34687bb11ec7b32d08feb45a7cb67fb6

commit 076f8e1b34687bb11ec7b32d08feb45a7cb67fb6
Author: Robert Kaplow <rkaplow@chromium.org>
Date: Fri Feb 02 21:20:28 2018

Revert "Test group policy for UKM."

This reverts commit 477b5b9f1c8315c88d385838e160b9b73781ff18.

Reason for revert: Flaky on Mac10.9 Tests

Original change's description:
> Test group policy for UKM.
> 
> Refactored the pref-setting logic out of metrics_reporting_state_browsertest in a way it could be reused in UKM. Setup a parametrized UKM test which tests the enabled/disabled group policy state based on prefs and verified service is enabled/disabled.
> 
> Bug:  805983 
> Change-Id: Ic303e4116826990e7780125f186b0028a8fd6a5e
> Reviewed-on: https://chromium-review.googlesource.com/895390
> Commit-Queue: Robert Kaplow <rkaplow@chromium.org>
> Reviewed-by: Steven Holte <holte@chromium.org>
> Reviewed-by: Scott Violet <sky@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#534086}

TBR=sky@chromium.org,rkaplow@chromium.org,holte@chromium.org

Change-Id: I95baa0b136424e1ca0bbc740479157024ca91a0a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug:  805983 
Reviewed-on: https://chromium-review.googlesource.com/900163
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Robert Kaplow <rkaplow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534157}
[modify] https://crrev.com/076f8e1b34687bb11ec7b32d08feb45a7cb67fb6/chrome/browser/BUILD.gn
[modify] https://crrev.com/076f8e1b34687bb11ec7b32d08feb45a7cb67fb6/chrome/browser/metrics/chrome_metrics_service_accessor.h
[modify] https://crrev.com/076f8e1b34687bb11ec7b32d08feb45a7cb67fb6/chrome/browser/metrics/metrics_reporting_state_browsertest.cc
[delete] https://crrev.com/97e9895c976520ff7fc128d0a43d37c7f4e4a59c/chrome/browser/metrics/testing/metrics_reporting_pref_helper.cc
[delete] https://crrev.com/97e9895c976520ff7fc128d0a43d37c7f4e4a59c/chrome/browser/metrics/testing/metrics_reporting_pref_helper.h
[modify] https://crrev.com/076f8e1b34687bb11ec7b32d08feb45a7cb67fb6/chrome/browser/metrics/ukm_browsertest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a5bcf62961ac93de536cf7ed0439ddd24cc433c4

commit a5bcf62961ac93de536cf7ed0439ddd24cc433c4
Author: Robert Kaplow <rkaplow@chromium.org>
Date: Mon Feb 12 16:24:52 2018

Reland of Test group policy for UKM.

Refactored the pref-setting logic out of metrics_reporting_state_browsertest in a way it could be reused in UKM. Setup a parametrized UKM test which tests the enabled/disabled group policy state based on prefs and verified service is enabled/disabled.

Bug:  805983 
Change-Id: Ib185814c45e2547cda984a032807416c4a2124df
Reviewed-on: https://chromium-review.googlesource.com/899956
Commit-Queue: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536093}
[modify] https://crrev.com/a5bcf62961ac93de536cf7ed0439ddd24cc433c4/chrome/browser/BUILD.gn
[modify] https://crrev.com/a5bcf62961ac93de536cf7ed0439ddd24cc433c4/chrome/browser/metrics/chrome_metrics_service_accessor.h
[modify] https://crrev.com/a5bcf62961ac93de536cf7ed0439ddd24cc433c4/chrome/browser/metrics/metrics_reporting_state_browsertest.cc
[add] https://crrev.com/a5bcf62961ac93de536cf7ed0439ddd24cc433c4/chrome/browser/metrics/testing/metrics_reporting_pref_helper.cc
[add] https://crrev.com/a5bcf62961ac93de536cf7ed0439ddd24cc433c4/chrome/browser/metrics/testing/metrics_reporting_pref_helper.h
[modify] https://crrev.com/a5bcf62961ac93de536cf7ed0439ddd24cc433c4/chrome/browser/metrics/ukm_browsertest.cc