Affected version

Provide at least the following information:

• Your OS and version: Manjaro (Linux 5.4.18-1)
• Affected GNOME Shell version: 3.34.2-1
• Does this issue appear in XOrg and/or Wayland: XOrg

Bug summary

When using Chromium based web browsers, such as Chrome and Brave, when the background is the desktop, the four corners of the browser window have a tiny black shadow that make the rounded browser corner look like square.

Interestingly, if the background is an app (as opposed to gnome-shell desktop), the black shadows are gone.

More interestingly, when the background is gnome-shell desktop, when you drag the window, the two corner that is "facing the wind" doesn't have this shadow. Let me explain: if you drag the window from left to right, the upper and lower right corners will not have the shadow; if you drag the window from right to left, the upper and lower left corners don't have the shadow.

Even more interestingly, if you just keep using the browser for like an hour, the shadows are gone. But if at this time you open a new browser window, the new window will have the same shadow issue.

Steps to reproduce

Open Brave or Google Chrome and make sure there's no app stacked behind it.

What happened

The shadows described above. I think this is a gnome-shell issue because I have tested this on many other DEs and onluy gnome-shell has this issue. I tried Budgie, KDE, and even Enlightenment, none of them have this issue (so it would be a bit unfair to say this is a Chromium problem).

What did you expect to happen

Window corners are rendered correctly.

Relevant logs, screenshots, screencasts etc.

Brave using GTK+ theme, black shadows at four corners. (Chrome has the same issue.)

Brave with an app stacked behind, no black shadows. (Chrome has the same issue.)

Brave with classic light theme, black shadows at four corners. (Chrome has the same issue.)

Brave with classic dark theme, black shadows at four corners. (Chrome has the same issue.)