createConfirmBtn_() {
    const confirmBtn = document.createElement('button');
    confirmBtn.className = 'blocklyModalBtn blocklyModalBtnPrimary';
    confirmBtn.textContent = Blockly.Msg['TYPED_VAR_MODAL_CONFIRM_BUTTON'];
    this.addEvent_(confirmBtn, 'click', this, this.onConfirm_);
    return confirmBtn;
  }
Create button in charge of creating the variable.
@returns {!HTMLButtonElement} The button in charge of creating a variable.
@protected