Findit identified the culprit r558079 with confidence 70.0% in the config "chromium.linux / Linux Tests (dbg)(1)"
based on the flakiness trend:

https://findit-for-me.appspot.com/waterfall/flake?key=ag9zfmZpbmRpdC1mb3ItbWVy3AELEhdNYXN0ZXJGbGFrZUFuYWx5c2lzUm9vdCKlAWNocm9taXVtLmxpbnV4L0xpbnV4IFRlc3RzIChkYmcpKDEpLzcxOTcxL25vdF9zaXRlX3Blcl9wcm9jZXNzX2Jyb3dzZXJfdGVzdHMvUlhoMFpXNXphVzl1UVhCcFZHVnpkRmRwZEdoTllXNWhaMlZ0Wlc1MFVHOXNhV041TGxkbFlsSmxjWFZsYzNSUWNtOTBaV04wWldSQ2VWQnZiR2xqZVE9PQwLEhNNYXN0ZXJGbGFrZUFuYWx5c2lzGAEM


Automatically posted by the findit-for-me app (https://goo.gl/Ot9f7N).
Feedback is welcome! Please use component Tools>Test>FindIt>Flakiness

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7af3bc79c29cbd9b3360154959856f451a7b25f4

commit 7af3bc79c29cbd9b3360154959856f451a7b25f4
Author: Timothy Loh <timloh@chromium.org>
Date: Mon May 14 04:59:44 2018

Revert "[Extensions Click-to-Script] Change default to allowing host permissions"

This reverts commit d9bf5454fb328977b5655f02f39f8722b6c28c3a.

Reason for revert: Breaks ExtensionApiTestWithManagementPolicy.WebRequestProtectedByPolicy on Linux Debug

https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=not_site_per_process_browser_tests&tests=ExtensionApiTestWithManagementPolicy.WebRequestProtectedByPolicy

https://logs.chromium.org/v/?s=chromium%2Fbuildbucket%2Fcr-buildbucket.appspot.com%2F8946590247605008336%2F%2B%2Fsteps%2Fnot_site_per_process_browser_tests%2F0%2Flogs%2FExtensionApiTestWithManagementPolicy.WebRequestProtectedByPolicy%2F0

Original change's description:
> [Extensions Click-to-Script] Change default to allowing host permissions
>
> Change the default behavior of the kRuntimeHostPermissions feature to
> allow extensions to have origin access, rather than defaulting to
> withholding permission. In the first stage of click-to-script, we don't
> want to change any defaults.
>
> Bug:  841099 
> Change-Id: Ibdcbfb0fd9ecc535af73a1bd9048e196eab135e1
> Reviewed-on: https://chromium-review.googlesource.com/1052684
> Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
> Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#558079}

TBR=rdevlin.cronin@chromium.org,karandeepb@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug:  841099 ,  842466 
Change-Id: Id37af8c43bbf30d8963852df9b29b58ff3ca5a53
Reviewed-on: https://chromium-review.googlesource.com/1056887
Commit-Queue: Timothy Loh <timloh@chromium.org>
Reviewed-by: Timothy Loh <timloh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558198}
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/extensions/api/developer_private/developer_private_api_unittest.cc
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/extensions/api/developer_private/extension_info_generator.cc
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/extensions/api/developer_private/extension_info_generator_unittest.cc
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/extensions/api/web_request/web_request_apitest.cc
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/extensions/extension_action_runner_browsertest.cc
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/extensions/extension_action_runner_unittest.cc
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/extensions/extension_context_menu_model_unittest.cc
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/extensions/extension_install_prompt_unittest.cc
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/extensions/permissions_updater.cc
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/extensions/permissions_updater_unittest.cc
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/extensions/scripting_permissions_modifier.cc
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/extensions/scripting_permissions_modifier.h
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/extensions/scripting_permissions_modifier_unittest.cc
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/browser/ui/extensions/blocked_action_bubble_browsertest.cc
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/test/data/extensions/api_test/developer/generated_output/behllobkkfkfnphdnhnkndlbkcpglgmj.json
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/test/data/extensions/api_test/developer/generated_output/bjafgdebaacbbbecmhlhpofkepfkgcpa.json
[modify] https://crrev.com/7af3bc79c29cbd9b3360154959856f451a7b25f4/chrome/test/data/extensions/api_test/developer/generated_output/hpiknbiabeeppbpihjehijgoemciehgk.json