Sidebar incorrectly overlapping with address bar

[kjljixx]

Preliminary Checks

• I have read and understood the important section above.
• I have searched existing issues and avoided creating duplicates.
• I am not filing an enhancement request.
• I have checked that this issue cannot be reproduced on Mozilla Firefox.
• I have checked that this issue can be reproduced once I removed all my Mods and Custom CSS.

What happened?

Sidebar is translucent for the address bar and incorrectly overlaps for the address bar (see attachments below).

Expected behavior

Sidebar content is fully "above" the address bar; its opacity should be 1

Actual behavior

Sidebar is translucent for the address bar.

Steps to reproduce

1. Make a new profile (or use an existing one)
2. In "Look & Feel" in about:settings, choose "multiple toolbars" and "hide both". Extend the sidebar to max width (or at least wide enough to cover some part of the address bar)
3. Close the window containing the profile
4. Re-open the profile. Click on the address bar in one tab, switch to another tab, then return to the original tab. Hover over the sidebar to see the issue.

Screenshots and videos

Version

1.15.5b

What platform are you seeing the problem on?

Windows - x64

What component is this issue related to?

Compact Mode

Relevant log output if applicable

[kjljixx]

The sidebar behaves fine when it is a brand new profile that was just made (after closing and re-opening the issue occurs). Idk if this helps, but it appears to be that in xulstore.json, opacity: 1; is stored in the navigator-toolbox style after the profile is made, but after the profile is re-opened, the opacity property is no longer in xulstore.