procedureDefHelper = function () {
  /**
   * An array of objects containing data about the args belonging to the
   * procedure definition.
   * @type {!Array<{
   *          model:Blockly.VariableModel,
   *          argId: string
   *       }>}
   * @private
   */
  this.argData_ = [];
  /**
   * Does this block have a 'STACK' input for statements?
   * @type {boolean}
   * @private
   */
  this.hasStatements_ = true;

  this.getInput('TOP').insertFieldAt(0, createPlusField(), 'PLUS');
}
Initializes some private variables for procedure blocks.
@this {Blockly.Block}