src/vs/workbench/browser/viewlet.ts/ViewletDescriptor/constructor
class ViewletDescriptor:	private constructor(
		ctor: IConstructorSignature0<Viewlet>,
		id: string,
		name: string,
		cssClass?: string,
		order?: number,
		requestedIndex?: number,
		readonly iconUrl?: URI
	) {
		super(ctor, id, name, cssClass, order, requestedIndex);
	}