Affected versions

• 88.0a1(2020-03-15), 87.0;

Affected platforms

• Windows 10, macOS 11.3

Steps to reproduce

1. Launch Firefox, access the Customize toolbar page;
2. Change to AlpenGlow theme;
3. Hover over the Downloads button (add it to toolbar before if not displayed);
4. Hover over the AutoHide tooltip;

Expected result

• tooltip properly displayed;

Actual result

• right border is not as rest of the lines for the tooltip;
• assumption: it might overlap with the search box doubling the intensity / transparency (moving it / the line clears);

Regression range

• First bad: 2020-08-21
• Pushlog: URL
• Visible after bug 1643776, adding it to regressor field for tracking purposes;

Additional notes

• attached screenshot to illustrate the issue;
• might be better in Theme or another section, please reassign if so; as this issue does not happen on Dark/Light theme.