Change font size of ComboBox dropdown

setRendererStyle solved it!

// add items to combobox

var dp:DataProvider = new DataProvider();

for each(var u:User in _userDb)

    dp.addItem({label:u._userName, data:u});

combo.dataProvider = dp;

var textFormat:TextFormat = new TextFormat();

textFormat.font = "Trebuchet MS";

textFormat.size = 26;

combo.textField.setStyle("textFormat", textFormat);

combo.rowCount = 10;

combo.dropdown.rowHeight = 40;

combo.dropdown.setRendererStyle("textFormat", textFormat);