Border being 'drawn' in content window when switching from split view tabs to normal tabs.

[ghost]

Description

Today I noticed there is a tiny border being draw in normal tabs after switch from a split view, it seems to match the border thickness of the border being used as an indication of which split view tab is the active one.

It happens in Vertical tabs as well, and in Private mode (where it is more noticeable for being darker).

It also disappears by switching from normal tab to normal tab, or resizing window or expanding/collapsing the VT.

Steps to reproduce

1. Create a split view
2. switch to normal tabs
3. there should be a border that disappears when you force some redrawing of content or you switch to other tabs.

Actual result

https://github.com/brave/brave-browser/assets/156715894/f07fc4f3-3814-4be5-9cd2-41d9e7e21465

Expected result

no border

Reproduces how often

Easily reproduced

Brave version (brave://version info)

1.69.45 Chromium: 126.0.6478.114 (Official Build) nightly (64-bit) Windows 11 Version 23H2 (Build 22631.3737)

Channel information

• [ ] release (stable)
• [ ] beta
• [ ] nightly

Reproducibility

• [ ] with Brave Shields disabled
• [ ] with Brave Rewards disabled
• [ ] in the latest version of Chrome

Miscellaneous information

No response

[ghost]

@sangwoo108 Also, when testing this I noticed I also get crashed anytime I just opened Brave. created a Split view and minimized the window.

I sent the crash reports 15cb1a00-bf2c-290c-0000-000000000000, 10cb1a00-bf2c-290c-0000-000000000000, 0bcb1a00-bf2c-290c-0000-000000000000.

Also, sometimes I get a crash when closing a split view in Private mode, they are not often, but I don't know if it happens when I switch monitors or when navigating and then the split views just stay split for a while. Don't think this has happened in normal windows, I don't remember. but I got them earlier so this should be the IDs shown by Brave when that crash happened: 05c81700-bf2c-290c-0000-000000000000, fcc71700-bf2c-290c-0000-000000000000 just so you know some crashes happen from time to time as well.