Main content window doesn't show all four rounded corners

[MadhaviSeelam]

Description

Found while testing #31645. The issue could be only windows issue as per @aguscruiz

Steps to Reproduce

1. Installed 1.61.60
2. launched Brave
3. opened brave://flags in a new tab
4. enabled #brave-web-view-rounded-corners
5. open brave.com in a new tab

Actual result:

Main content window doesn't show all four rounded corners. Rounded corners appear only left side of the main content window. Sidebar panel shows rounded corners as well.

example	example

Expected result:

Main content window should show all four rounded corners and should match to the Figma.

Reproduces how often:

Easily

Brave version (brave://version info)

Brave | 1.61.61 Chromium: 119.0.6045.105 (Official Build) beta (64-bit)
-- | --
Revision | 6bbedb0b809f83b08334ffa36b1ea9df92e86245
OS | Windows 11 Version 22H2 (Build 22621.2428)

Version/Channel Information:

• Can you reproduce this issue with the current release? N/A
• Can you reproduce this issue with the beta channel? Yes
• Can you reproduce this issue with the nightly channel? N/A

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information:

@rebron @zenparsing
cc: @aguscruiz

[zenparsing]

Is this because of the scrollbar on Windows? @aguscruiz

[aguscruiz]

Oh, could that be it? I guess there's no way to fix that then, right?

[LaurenWags]

Reproduces on Linux as well.

Brave	1.61.82 Chromium: 119.0.6045.163 (Official Build) beta (64-bit) 
Revision	c5d19b3a31e7e3ddaaa1fa2ea52b9338003e754e
OS	Linux