message: change ViewState specialElements to be readonly
diff: @@ -110,13 +110,16 @@ export class SpecialElements {
  * Subclasses of ViewDefinition determine which model(s) are viewed.
  */
  export abstract class ViewState extends ElementState {
  - protected _special?: SpecialElements;
  protected _noQuery: boolean = false;
  protected _featureOverridesDirty: boolean = false;
  protected _selectionSetDirty: boolean = false;
  public static get className() { return "ViewDefinition"; }
  public description?: string;
  public isPrivate?: boolean;
  +
  + /** Get the set of special elements for this ViewState. */
  + public readonly specialElements: SpecialElements = new SpecialElements();
  +
  protected constructor(props: ViewDefinitionProps, iModel: IModelConnection, public categorySelector: CategorySelectorState, public displayStyle: DisplayStyleState) {
  super(props, iModel);
  this.description = props.description;
  @@ -145,9 +148,6 @@ export abstract class ViewState extends ElementState {
  public get backgroundColor(): ColorDef { return this.displayStyle.backgroundColor; }
  - /** Get the set of special elements for this ViewState. */
  - public get specialElements(): SpecialElements { return this._special!; }
  -
  /** Get the list of elements that are never drawn */
  public get neverDrawn(): Id64Set { return this.specialElements.never; }
  