src/vs/workbench/contrib/themes/browser/themes.contribution.ts/toEntry
function toEntry(theme: IWorkbenchTheme): ThemeItem {
	const item: ThemeItem = { id: theme.id, theme: theme, label: theme.label, description: theme.description };
	if (theme.extensionData) {
		item.buttons = [configureButton];
	}
	return item;
}