Do you love the dark theme, Firefox developer edition comes with built-in? FYI, this beauty is available for Nightly and dev channels only, but for stable and beta users, Mozilla allows to activate it by using Developer Edition theme enabler add-on. If you’re using Chrome, you don’t find similar type of theme in the Web Store to install. Finally, its here, an extension with name Developer Edition Dark almost dresses up Chrome like DE dark.
To revert to the default theme, visit Chrome Settings > Appearance, click on ‘Reset to default theme’, changes will be applied immediately without need to restart the browser.