[Bug]: Rounder corners colors stand out a little

[Minnona]

Pre-Submission Checklist

• [X] I have checked the existing/closed issues to ensure this issue has not already been reported.
• [X] I am using the latest supported version of the browser.
• [ ] I have tried disabling all browser extensions/add-ons to rule out interference from these.
• [ ] I have tried clearing the browser cache and cookies.
• [ ] I have tried to create a new profile and the issue still occurs.
• [X] I have provided detailed step-by-step instructions on how to reproduce the issue.
• [X] I have included relevant screenshots or console outputs.
• [ ] I have checked this problem is not ocurring in the latest version of Firefox ESR.
• [X] This issue is specific to this browser and does not occur in other browsers.

Bug Summary

Hey, I noticed rounded corners have a different color compared to the rest of toolbar in both dark and light themes, would be nice if they match the color of neighboring borders.

Reproduction Steps

1. Enable rounder corners
2. Crawl into a ball and cry

Expected Behavior

Colors of corners matching with the rest of the browser

Actual Behavior

Rounder corners stand out

Screenshots

Browser Version

11.13.3 (64-bit)

Operating System

Windows 11

Additional Context

No response

[surapunoyousei]

This is a limitation because border-radious cannot be used. I don't care that much about it, so I don't intend to fix it.