Private tab animation sometimes gets stuck

[cndouglas]

Description

Sometimes, when I'm creating new private tabs with Cmd+Click, the animation gets stuck, and a dark purple gradient appears on the right side of the tab. Mousing over the tab resets the appearance and fixes the problem.

It usually happens with an inactive tab immediately to the right of the active tab. After it happens in a particular window, it usually does not happen again.

Steps to Reproduce

1. Open Brave, open a new private tab, and navigate to any link (e.g. GitHub).
2. Use Cmd+Click to open links in new private tabs.

Actual result:
This is what the bug looks like:

Note that the first tab is the active tab. The second tab is inactive but has a partial active gradient.

Expected result:
The inactive tab should look like this:

Reproduces how often:
I run into it at least once every time I'm using private tabs.

Brave Version

about:brave info:
Brave: 0.20.42
V8: 6.4.388.41
rev: 096c7cb
Muon: 4.8.2
OS Release: 17.4.0
Update Channel: Release
OS Architecture: x64
OS Platform: macOS
Node.js: 7.9.0
Brave Sync: v1.4.2
libchromiumcontent: 64.0.3282.140

Reproducible on current live release:
Yes, 0.20.42.

Additional Information

Maybe related: #12721

[srirambv]

Possibly related to #11249 as well. The same fix might fix this as well

[cndouglas]

Appears fixed in 0.23.105 (current release).