How are the new taller table header rows with extra sorting functionality in iTunes implemented?

In iTunes 10 Apple switched to a taller table header with a slightly different visual appearance, where the column dividers don't reach the top of the row, and certain c开发者_开发技巧ells have extended sorting functionality when clicked.

Here is what i'm refering to:

Are these a custom control created specifically for iTunes or can they be uses by other applications?

iTunes is a Carbon app. It doesn't use NSTableView. You can be sure that's custom.