Currently, Android's NavigationWindow only supports opening Ti.UI.Window objects. It does not currently support opening a TabGroup like iOS. We should add TabGroup support for parity.
The NavWindowTabGroupTest.js file sets up a TabGroup as the 1st window in a NavigationWindow and can launch a child Window from each tab. (Currently crashes with an exception.)
The NavWindowChildTabsTest.js has a Window as the 1st window in a NavigationWindow which opens a TabGroup as a child. This is a separate test case is needed since the open handling is different. (Currently shows a blank tab group with no tabs.)
iOS does not currently support displaying a TabGroup "title" in the NavigationWindow title bar. This is because our TabGroup does not currently support a "title" property. On Android, TabGroup does have an undocumented "title" property which would allow this to work. (Perhaps we should add "title" property support to iOS in the future.)