src/vs/editor/common/config/editorOptions.ts/EditorStringEnumOption/constructor
class EditorStringEnumOption:	constructor(id: K, name: PossibleKeyName<V>, defaultValue: V, allowedValues: ReadonlyArray<V>, schema: IConfigurationPropertySchema | undefined = undefined) {
		if (typeof schema !== 'undefined') {
			schema.type = 'string';
			schema.enum = <any>allowedValues;
			schema.default = defaultValue;
		}
		super(id, name, defaultValue, schema);
		this._allowedValues = allowedValues;
	}