Affected versions

• Firefox 69 Beta 9
• Firefox 69 beta 9 Snap build
• latest Nightly 70.0a1 (2019-07-29)
• Firefox 68.0.1
• Firefox 67.0
• Firefox 58.0

Affected platforms

• Ubuntu 18.04 x64
• Ubuntu 16.04 x86

Preconditions

• "Downloads" button is moved to Overflow Menu.

Steps to reproduce

1. Launch Firefox with a clean profile and open a Private window.
2. In Private window, go to this link and download two items.
3. Open Overflow Menu -> Downloads.
4. Click on "Show All Downloads".

Expected result

• "about:downloads" is opened in a new tab and the Overflow Menu is closed.

Actual result

• "about:downloads" is opened in a new tab, but the Overflow Menu is NOT closed. Please see "issue.mp4" attachment.

Regression range

• It's not a recent regression since the issue is reproducible with Firefox 58.0. I will search for regression range ASAP.

Additional notes

• This is an Ubuntu specific issue. On Windows 10 and macOS 10.13, the issue is not reproducible.

Bugbug thinks this bug is a regression, but please revert this change in case of error.

My Firefox doesn't like the video format, but I could see it with another browser.
This is not a top priority because anyway moving the downloads button in the overflow is not something common, also considered it's a button that auto-hides, not taking any space when unused. Adding the linux-only fact, it is likely to affect a very tiny population slice.
Patches/suggestions would be welcome.

It seems the issue is not a regression since it's reproducible with Firefox 57.0a1, 2017-09-13 (buildID: 20170913220121) when the "Show All Downloads" button was introduced in Overflow Menu -> Downloads.