Gap between url bar and tab content in GTK theme.

[Cyliann]

Description

If the chosen theme is GTK, there's a smal gap between url bar and tab content and I can see my wallpeper through it.

Steps to Reproduce

1. Use GTK theme
2. Launch picom (or any other compositor which allows transparency. I have Brave transparency set to 100% so it should be fully opaque)
3. Notice the gap

Actual result:

GTK theme

Classic theme

Expected result:

No gap.

Reproduces how often:

Every time

Brave version (brave://version info)

Version: 1.52.130 Chromium: 114.0.5735.198 (Official Build) (64-bit) Revision: c3029382d11c5f499e4fc317353a43d411a5ce1c-refs/branch-heads/5735@{#1394 OS: Linux

Version/Channel Information:

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

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? No
• Does the issue resolve itself when disabling Brave Rewards? No
• Is the issue reproducible on the latest version of Chrome? Yes, but the gap is smaller

Miscellaneous Information:

[uzuto]

This issue still hasn't been resolved.