Browser-laptop: Other tabs are forced to pinned-tab size after closing tab that used to be pinned

[kjozwiak]

Test plan

https://github.com/brave/browser-laptop/pull/11436#issuecomment-360345949

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Description

When you're closing a tab that was perviously pinned and has been unpinned, the tab next to it will quickly appear as a pinned tab until the mouse is moved. Please see the GIF example below.

You'll also see the following error message in the terminal but this also appears in 0.19.139 which is the latest released version:

[31659:31659:0124/195057.560341:ERROR:CONSOLE(0)] "Unchecked runtime.lastError while running guestViewInternal.destroyGuest: Unknown error.", source: chrome://brave/usr/lib/brave-beta/resources/app.asar/app/extensions/brave/index.html (0)

Steps to Reproduce

1. launch 0.20.20
2. open a new tab and visit motorsport.com (make sure it's the only tab opened)
3. open a new tab and visit reddit.com (you should now have two tabs opened)
4. pin the second tab (reddit.com)
5. unpin reddit.com and close the tab
6. you should have a single tab left opened (motorsport.com)
7. open a new tab and visit reddit.com (you should now have two tabs opened)
8. pin the second tab (reddit.com)
9. unpin reddit.com and close the tab (don't move your mouse once you click close)

Actual result:

Expected result:

The second tab shouldn't appear as pinned when the first tab that used to be pinned is closed.

Reproduces how often:

100% reproducible using the above STR mentioned above.

Brave Version

about:brave info:

Brave: 0.20.20
V8: 6.4.388.29
rev: df8eaf7e05a802d1e49c189c67ad0c8a6c554db2
Muon: 4.7.3
libchromiumcontent: 64.0.3282.99

Reproducible on current live release:

I couldn't reproduce this under 0.19.139 after about 5 minutes of trying. Easily reproducible using 0.20.20.

Additional Information

CCing @petemill

[petemill]

I can reproduce in 0.20. I cannot reproduce on master / 0.22 / 0.21, so I'll look for a fix directly to 0.20.

[petemill]

Fixed in #11436