Affected versions

• Firefox 90.0b3
• Firefox 91.0a1

Affected platforms

• Windows 8.1

Steps to reproduce

1. Launch Firefox
2. Enter customize mode and set the dark theme
3. Unfocus the browser

Expected result

• Titles are visible on tabs if the browser is unfocused

Actual result

• Titles on tabs are barely visible if the browser is unfocused

Regression range

• Will see for a regression

Additional notes

• The issue can be seen in the attachment

Do you have a regression range yet?

The component has been changed since the backlog priority was decided, so we're resetting it.
For more information, please visit auto_nag documentation.

Here's the regression for this between 2021-04-06 and 2021-04-07

Bug 1700109 - Enable main Proton pref by default in Nightly

This sets browser.proton.enabled to true by default in Nightly. This is the first
wave of Proton changes.

Pushlog: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=edf8a5f5141f4603a0494a5a7ce377514c1f6ff4&tochange=90a48858e199adfa16947c311265da00be93ccfd

(In reply to Catalin Sasca, QA [:csasca] from comment #3)

Here's the regression for this between 2021-04-06 and 2021-04-07

Can you please try bisecting with the browser.proton.enabled pref set to true to find the actual culprit?

Sure thing, so after bisecting, it seems that there were some changes on toolbar between 2021-03-26 and 2021-03-27. While on builds from 26 and before, the toolbar will look like in the attachment I will add here.

The pushlog url between those two builds is: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=0d037f6863771e24c74eca997030f8296af24af8&tochange=6e52d2a6585df26518f5d6e9de03b2486e8f8f4c.

Mozregression will point to:
Backed out 4 changesets (bug 1696041) for causing gecko decision task failure. CLOSED TREE

Backed out changeset a0b814900c36 (bug 1696041)
Backed out changeset d380f63d1926 (bug 1696041)
Backed out changeset 7699e68d6822 (bug 1696041)
Backed out changeset 1c4906861110 (bug 1696041)

Hope this helps!

Bug 1700873 maybe, from the pushlog in comment 5?

This bug happened because we override the existing :root rule with transparent !important. I verified the fix with a Windows 8.1 VM and verified that bug 1700873 does not recur.

This was fixed in bug 1724956.

The patch landed in nightly and beta is affected.
:harry, is this bug important enough to require an uplift?
If not please set status_beta to wontfix.

For more information, please visit auto_nag documentation.

Bug 1724956 was uplifted so I'm clearing needinfo.