Make proper native theme observer gets native theme change noti

[simonhong]

Chromium supports dark theme on Windows since C74.
So, brave should get proper native theme change noti when os theme
changes because brave uses two native theme - default and native theme
dark aura.

Fix brave/brave-browser#4059

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Windows
  • macOS
  • Linux
• Verified that these changes pass automated tests (npm test brave_unit_tests && npm test brave_browser_tests && npm run test-security) on
  • Windows
  • macOS
  • Linux
• Verified that all lint errors/warnings are resolved (npm run lint)
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone

Test Plan:

Specified in brave/brave-browser#4059

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

[simonhong]

kindly ping..

[simonhong]

@petemill @kjozwiak I think it would be good to have this fix in our next stable release.

[kjozwiak]

@simonhong after discussing with @srirambv and @rebron, we decided it's too late to get this into 0.63.x as we're basically releasing in a few days. Even though not ideal, there's a workaround of restarting the browser. However, we agreed that this should go into 0.64.x. Can you get the appropriate PR/Uplift requests created?

[simonhong]

@kjozwiak yup! I'll make uplift PR up to 0.64.x after @petemill finishes review.

[petemill]

Apologies for the delay, thanks for the fix @simonhong

[simonhong]

Apologies for the delay, thanks for the fix @simonhong

@petemill NP! thanks for review :)