Once all the remaining patches for test tweaks / fixes have landed, this
patch should be green on try. Couple test annotation changes:

• clip-003.html fails the same way it fails on mac (odd, but couldn't
  repro...). I'll try to dig a bit more before calling it a day.

• radiobutton-min-size starts behaving like every other platform.

• Event-dispatch-redispatch and baseline-alignment-and-overflow start
  passing.

• Couple minor fuzzy annotations (one was backwards, the other was
  missing).

https://hg.mozilla.org/mozilla-central/rev/d9e5a018312e
https://hg.mozilla.org/mozilla-central/rev/d4a60b3559cf
https://hg.mozilla.org/mozilla-central/rev/31841a09424b
https://hg.mozilla.org/mozilla-central/rev/866ccb0fbb91

I suspect this change caused Bug 1689931 - [regression?] Scrollbar is no longer themable under Linux in Firefox Nightly 87.0a1 (2021-01-31)

== Change summary for alert #28590 (as of Tue, 02 Feb 2021 13:19:39 GMT) ==

Improvements:

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=28590

== Change summary for alert #28600 (as of Wed, 03 Feb 2021 10:46:38 GMT) ==

Improvements:

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=28600

This again broke scrollbar arrows on Linux Manjaro for me.

History:

• my first bug https://bugzilla.mozilla.org/show_bug.cgi?id=1579631
• duplicated to https://bugzilla.mozilla.org/show_bug.cgi?id=1504787#c10 and about:config solution
• regression after layout.css.scrollbar-color.enabled was removed https://bugzilla.mozilla.org/show_bug.cgi?id=1641324#c13
• userContent solution https://bugzilla.mozilla.org/show_bug.cgi?id=1645676

[rdk@on ~]$ mozregression --good  2021-01-28 -p /media/on/doc/tmplc9zis4t.mozrunner/ --pref security.sandbox.content.level:0 ^C
...

12:35.66 INFO: Downloading build from: https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/bdhjyENSSyixx_ft42Ewfw/runs/0/artifacts/public%2Fbuild%2Ftarget.tar.bz2
===== Downloaded 100% =====
13:24.27 INFO: Running autoland build built on 2021-02-03 11:59:17.781000, revision d6481478
13:37.20 INFO: Launching /tmp/tmp_ehuocfz/firefox/firefox
13:37.20 INFO: Application command: /tmp/tmp_ehuocfz/firefox/firefox --allow-downgrade -profile /tmp/tmp4nmg7yyo
13:37.21 INFO: application_buildid: 20210130161107
13:37.21 INFO: application_changeset: d6481478a8e01366fb3af2e0788aa6666429d5f1
13:37.21 INFO: application_name: Firefox
13:37.21 INFO: application_repository: https://hg.mozilla.org/integration/autoland
13:37.21 INFO: application_version: 87.0a1
Was this integration build good, bad, or broken? (type 'good', 'bad', 'skip', 'retry', 'back' or 'exit' and press Enter): good
13:46.72 INFO: Narrowed integration regression window from [a3231eeb, d9e5a018] (3 builds) to [d6481478, d9e5a018] (2 builds) (~1 steps left)
13:46.73 INFO: No more integration revisions, bisection finished.
13:46.73 INFO: Last good revision: d6481478a8e01366fb3af2e0788aa6666429d5f1
13:46.73 INFO: First bad revision: d9e5a018312eccf63acbda32759d90e2f92175d7
13:46.73 INFO: Pushlog:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=d6481478a8e01366fb3af2e0788aa6666429d5f1&tochange=d9e5a018312eccf63acbda32759d90e2f92175d7

It's kind of expected, see bug 1676057. I guess we could add a pref to allow using scrollbar buttons on GTK with windows-looking scrollbars. Please file a bug and ni? me and I can look into it.