The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6d6838d4049b01fd25d6c34bc3863ef85a8278f6

commit 6d6838d4049b01fd25d6c34bc3863ef85a8278f6
Author: Charles Harrison <csharrison@chromium.org>
Date: Tue Mar 20 15:37:29 2018

[tab-under] Add pref to turn feature off

A followup will hook this pref with a new enterprise policy to turn the
feature off.

Bug:  823700 
Change-Id: I06096460a372941ba06f3bf3e9cc63b9084f82cd
Reviewed-on: https://chromium-review.googlesource.com/970729
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Commit-Queue: Charlie Harrison <csharrison@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544375}
[modify] https://crrev.com/6d6838d4049b01fd25d6c34bc3863ef85a8278f6/chrome/browser/prefs/browser_prefs.cc
[modify] https://crrev.com/6d6838d4049b01fd25d6c34bc3863ef85a8278f6/chrome/browser/ui/blocked_content/popup_opener_tab_helper_unittest.cc
[modify] https://crrev.com/6d6838d4049b01fd25d6c34bc3863ef85a8278f6/chrome/browser/ui/blocked_content/tab_under_navigation_throttle.cc
[modify] https://crrev.com/6d6838d4049b01fd25d6c34bc3863ef85a8278f6/chrome/browser/ui/blocked_content/tab_under_navigation_throttle.h
[modify] https://crrev.com/6d6838d4049b01fd25d6c34bc3863ef85a8278f6/chrome/common/pref_names.cc
[modify] https://crrev.com/6d6838d4049b01fd25d6c34bc3863ef85a8278f6/chrome/common/pref_names.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1d821a0ca6a2585cc74d608b547daca8334de194

commit 1d821a0ca6a2585cc74d608b547daca8334de194
Author: Charlie Harrison <csharrison@chromium.org>
Date: Thu Mar 22 04:22:50 2018

[tab-under] hook up pref with enterprise policy

This CL hooks into the pref added in [1] which controls tab-under
protection. This allows enterprises to turn off tab-under protection.

[1]: https://chromium-review.googlesource.com/c/chromium/src/+/970729

Bug:  823700 
Change-Id: I49d32aa5f0a270e52bace8f9d509d996589d1ad5
Reviewed-on: https://chromium-review.googlesource.com/970846
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Charlie Harrison <csharrison@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544974}
[modify] https://crrev.com/1d821a0ca6a2585cc74d608b547daca8334de194/chrome/browser/policy/configuration_policy_handler_list_factory.cc
[modify] https://crrev.com/1d821a0ca6a2585cc74d608b547daca8334de194/chrome/browser/ui/blocked_content/tab_under_blocker_browsertest.cc
[modify] https://crrev.com/1d821a0ca6a2585cc74d608b547daca8334de194/chrome/test/data/policy/policy_test_cases.json
[modify] https://crrev.com/1d821a0ca6a2585cc74d608b547daca8334de194/components/policy/resources/policy_templates.json
[modify] https://crrev.com/1d821a0ca6a2585cc74d608b547daca8334de194/tools/metrics/histograms/enums.xml