DevTools - "Panel layout" preference is no longer saved

Description

The DevTools settings for the “Panel layout” preference (DevTools > Settings > Preferences > Appearance > Panel Layout) is no longer saved or reset to the default value each time the DevTools are opened. This behavior occurs in the normal and private browser window.

Steps to Reproduce

1. Open a website (e.g. https://brave.com/)
2. Open the DevTools (for example via the keyboard shortcuts) macOS: <kbd>Command</kbd>+<kbd>Option</kbd>+<kbd>I</kbd> Win: <kbd>Control</kbd>+<kbd>Shift</kbd>+<kbd>I</kbd>
3. Open the DevTools settings (gear-icon in the upper right)
4. Change the selected default value for the Panel layout preference from auto to horizontal
5. Close the DevTools settings
6. The panels under Elements are now horizontally aligned
7. Close the DevTools
8. Reopen the DevTools
9. The panels under Elements are aligned automatically and the setting for Panel layout is back to auto

Actual result:

After changing the Panel layout preference default value, closing and reopening the DevTools the selected value is reset to the default value auto.

Expected result:

After changing the Panel layout preference, closing and reopening the DevTools the previous selected value is still set and the Elements panels are still aligned accordingly.

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

Brave | 1.32.106 Chromium: 96.0.4664.45 (Official Build) (x86_64) Revision | 76e4c1bb2ab4671b8beba3444e61c0f17584b2fc-refs/branch-heads/4664@{#947} OS | macOS Version 12.0.1 (Build 21A559)

Version/Channel Information:

• Can you reproduce this issue with the current release? YES
• Can you reproduce this issue with the beta channel? N/A
• Can you reproduce this issue with the nightly channel? N/A

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? No
  • This behavior does not occur in the latest Chrome version (96.0.4664.45)

[xyzith]

I have same problem. Add custom device won’t save either.

[bsclifton]

Should be fixed with https://github.com/brave/brave-core/pull/12600 - duplicate of https://github.com/brave/brave-browser/issues/20491

Fix is in Nightly and will be uplifted to Beta and Release channels. Thanks for your patience, folks 😄