P: Script UI Listbox columns do not work anymore

Just updated from CC 2014 to CC 2015 and my scripts broke (https://github.com/gimblll/GBL-Textur...). After debugging I've narrowed it down to the use of a listbox with columns. For some reason the new version fails to create the columns.

I narrowed it down to a short example. This fails to produce columns in 2015. And if the commented line is uncommented, I get a "Not implemented" error. (And all this works in 2014.)

var win = new Window("dialog", "Test Window");

var panel = win.add("panel");
panel.alignChildren = ["fill", undefined]
panel.preferredSize = [1000, undefined];

var list = panel.add("listbox", undefined, undefined, {
numberOfColumns: 2,
showHeaders: true,
columnTitles: ["Id", "Resize", ],
});

list.preferredSize = [undefined, 100];

var item1 = list.add ("item", "Test1");
// item1.subItems[0].text = "Test2";

win.show();