The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/20e47eec85cb90c52752d2298f1db9ddb9e57c6d

commit 20e47eec85cb90c52752d2298f1db9ddb9e57c6d
Author: Charlie Harrison <csharrison@chromium.org>
Date: Tue May 08 02:41:51 2018

[tab-under] Control via the popup block setting

Some of the new redirect-style interventions require a sticky
permission bit. There is a plan to govern these interventions via
the popup setting.

This CL avoids tab-under blocking if the popup setting is set to
ALLOW.

Follow-up CLs make modifications to the UI to make this behavior
understandable to users. See go/popup-redirect-unification-ui for
mocks.

Bug:  840351 
Change-Id: I14f8a30cf8528a98d203cec89bf06d94fc64947e
Reviewed-on: https://chromium-review.googlesource.com/1042106
Commit-Queue: Charlie Harrison <csharrison@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556655}
[modify] https://crrev.com/20e47eec85cb90c52752d2298f1db9ddb9e57c6d/chrome/browser/ui/blocked_content/tab_under_blocker_browsertest.cc
[modify] https://crrev.com/20e47eec85cb90c52752d2298f1db9ddb9e57c6d/chrome/browser/ui/blocked_content/tab_under_navigation_throttle.cc
[modify] https://crrev.com/20e47eec85cb90c52752d2298f1db9ddb9e57c6d/chrome/browser/ui/blocked_content/tab_under_navigation_throttle.h