On the access management page while using Chrome Version 24.0.1312.45 beta on arch linux the "admin" choice is not visible for a person previously added to a project. The only choices are to set a user to "read" or "write" status. Users previously set to admin status show up only as lacking "read" and "write" status.
The attached image shows this problem on a repository in which I am the owner and one other user is also an admin.
Edit: This problem doesn't occur on version 18.104.22.1688.0 of chromium.