As you likely noticed, support for styling progress elements varies by the browser.
Doing so requires vendor prefixes and a fallback for older browsers if you want things to look consistant.
To achieve your desired look and keep things consistent it might be easiest to create your own
progress bar by using sprites or a HTML solution with a custom plugin.
The fiddle you sent would use the later.
If your target export is nw.js you can safely ignore that advice and use some of the webkit prefixes from the link bellow.
Here's an article that covers the process and pitfalls of styling progress elements
About loading CSS with the web font action,
The CSS is included for the lifetime of your app, so it would be best moved to the loading layout.
Your HTML elements may show without style for an instant while the stylesheet is fetched.
It's worth asking Ashley for 'On web font loaded' and '.. failed' conditions if this is a problem.
To apply different styles based on events you can add/remove class's to your element (with jquery for example).
It's one of the default themes
- View/Style/Visual Studio styles/Visual Studio Dark 2012
- File/Preferences/Colors/Choose theme/Default
The style on the tabs won't seem to change until you restart the editor.