Update location bar when brave theme changes

[simonhong]

Close brave/brave-browser#974

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).
• 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/Needed or QA/No-QA-Needed) to include the closed issue in milestone

Test Plan:

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

[petemill]

This works to fix the specific issue for LocationBar, since it does not use ThemeService properties but uses OmniboxTheme which can also change between light and dark. However, as discussed, this does not fix the view items which use properties from NativeTheme, which also has different light and dark implementations.

One possible strategy to solve both cases is to simply call OnNativeThemeChanged instead or in addition to OnThemeChanged for all Views, then everything should re-paint properly when our theme mode preference is changed.

Here's an example of why we want OnNativeThemeChanged to fire for all views

void Label::OnNativeThemeChanged(const ui::NativeTheme* theme) {
  UpdateColorsFromTheme(theme);
}

[simonhong]

@petemill Location bar seems changed properly when theme changed.

[petemill]

LGTM - thanks

[petemill]

0.55.x f99debb