message: Add QuestionMatrixDropdownModelBase.defaultCellType static property
diff: @@ -400,7 +400,7 @@ export class MatrixDropdownColumn extends Base implements ILocalizableOwner {
  protected calcCellQuestionType(): string {
  if (this.cellType !== "default") return this.cellType;
  if (this.colOwner) return this.colOwner.getCellType();
  - return "dropdown";
  + return QuestionMatrixDropdownModelBase.defaultCellType;
  }
  protected updateTemplateQuestion() {
  var prevCellType = this.templateQuestion
  @@ -844,6 +844,7 @@ export class QuestionMatrixDropdownModelBase
  MatrixDropdownColumn
  >
  implements IMatrixDropdownData {
  + public static defaultCellType = "dropdown";
  public static addDefaultColumns(matrix: QuestionMatrixDropdownModelBase) {
  var colNames = QuestionFactory.DefaultColums;
  for (var i = 0; i < colNames.length; i++) matrix.addColumn(colNames[i]);
  @@ -939,7 +940,10 @@ export class QuestionMatrixDropdownModelBase
  * Use this property to change the default cell type.
  */
  public get cellType(): string {
  - return this.getPropertyValue("cellType", "dropdown");
  + return this.getPropertyValue(
  + "cellType",
  + QuestionMatrixDropdownModelBase.defaultCellType
  + );
  }
  public set cellType(val: string) {
  val = val.toLowerCase();
  