Fix the issue with "Show pinned tabs in all windows" option

[jagadeshjai]

• Show 'Show pinned tabs in all windows' option in setting page only when its feature flag is enabled.

Resolves brave/brave-browser#40675

Outcome

brave_shared_pinned_tabs_fix.webm

Submitter Checklist:

• I confirm that no security/privacy review is needed and no other type of reviews are needed, or that I have requested them
• [x ] There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally:
  • npm run test -- brave_browser_tests, npm run test -- brave_unit_tests wiki
  • npm run presubmit wiki, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

• For the test plan, kindly refer to the issue description's Fix verification.

[jagadeshjai]

@mkarolin / @fallaciousreasoning Could you please take a look at this PR?

[fallaciousreasoning]

Looks great, I'll kick off CI!

[fallaciousreasoning]

Kicked of CI here: #25382

[jagadeshjai]

Thanks for the review @fallaciousreasoning ❤️

[jagadeshjai]

Thanks for merging @mihaiplesa 😄 !

[LaurenWags]

Verified with

Brave | 1.71.66 Chromium: 128.0.6613.120 (Official Build) nightly (x86_64)
-- | --
Revision | 87ca8e6d850b0c0682c49be9014a62fdfad3face
OS | macOS Version 13.6.9 (Build 22G830)

Used 1.69.162 Chromium: 128.0.6613.120 and steps from the issue to reproduce

1. Start the browser and navigate to brave://flags
2. Search for brave-shared-pinned-tabs and verify that it's set to disabled (default).

3. Navigate to brave://settings/appearance and scroll down to the [Tabs] section
4. Enable "Show pinned tabs in all windows" setting

5. Navigate to brave.com
6. Right-click on the tab and select Pin
7. Observe the tab is now pinned

8. Open a new browser window via the hamburger menu
9. Observe the new window has no pinned tabs.

Using 1.71.66 Chromium: 128.0.6613.120 and steps from the issue, confirmed setting is not displayed when flag is off and spot checked setting worked as expected:

1. Start the browser and navigate to brave://flags
2. Search for brave-shared-pinned-tabs and verify that it's set to disabled (default).

3. In another tab, navigate to brave://settings/appearance and scroll down to the [Tabs] section
4. Verify that there's no "Show pinned tabs in all windows" setting shown

5. In the first tab, enable the brave-shared-pinned-tabs flag and click Relaunch button.

6. Once the browser restarts, navigate to brave://settings/appearance and scroll down to the [Tabs] section
7. Verify that the "Show pinned tabs in all windows" setting is now shown and disabled (by default)

8. Navigate to brave.com
9. Right-click on the tab and select Pin
10. Observe the tab is now pinned

11. Open a new browser window via the hamburger menu
12. Verify the new window has no pinned tabs.

13. Enable the "Show pinned tabs in all windows" in the Settings -> Appearance [Tabs]

14. Open a new browser window via the hamburger menu
15. Verify the new window has brave.com pinned tab.