It relies on various hacky patches to e.g. gtk+2.x. There's an extension to add it to GNOME 3, but it still relies on those patches. Ubuntu planned to remove as

It relies on various hacky patches to e.g. gtk+2.x. There's an extension to add it to GNOME 3, but it still relies on those patches. Ubuntu planned to remove as many patches as possible. So with the extension and those patches it will currently be possible, but might not in future when they remove the patches. So basically: maybe yes, maybe no.