showKeyringMgmtForm_(formId) {
    goog.array.forEach(
        this.getElement().querySelectorAll('div[id]'), function(elem) {
          goog.dom.classlist.add(elem, constants.CssClass.HIDDEN);
        });

    goog.dom.classlist.remove(
        goog.dom.getElement(formId), constants.CssClass.HIDDEN);

    if (formId == constants.ElementId.GENERATE_KEY_FORM) {
      var signupForm =
          goog.dom.getElement(constants.ElementId.GENERATE_KEY_FORM);
      var signupPrompt = goog.dom.getElement(constants.ElementId.SIGNUP_PROMPT);
      var cancelButton =
          goog.dom.getElementByClass(constants.CssClass.HIDDEN, signupForm);
      var keyringOptions =
          goog.dom.getElement(constants.ElementId.KEYRING_OPTIONS_DIV);

      goog.dom.classlist.add(signupPrompt, constants.CssClass.HIDDEN);
      goog.dom.classlist.remove(cancelButton, constants.CssClass.HIDDEN);
      goog.dom.classlist.remove(keyringOptions, constants.CssClass.HIDDEN);
    }

    if (formId == constants.ElementId.KEYRING_PASSPHRASE_CHANGE_DIV ||
        formId == constants.ElementId.KEYRING_PASSPHRASE_CONFIRM_DIV) {
      var inputElem = goog.dom.getElement(formId).querySelector('input');
      inputElem.value = '';
      inputElem.focus();

      // Pressing Enter triggers the next step.
      var keyboardHandler = new goog.ui.KeyboardShortcutHandler(inputElem);
      keyboardHandler.registerShortcut('enter', goog.events.KeyCodes.ENTER);
      this.getHandler().listenOnce(
          keyboardHandler,
          goog.ui.KeyboardShortcutHandler.EventType.SHORTCUT_TRIGGERED,
          ((formId == constants.ElementId.KEYRING_PASSPHRASE_CHANGE_DIV) ?
               this.confirmKeyringPassphrase_ :
               this.updateKeyringPassphrase_));
    }
  }
Shows the selected keyring management form and hides all other such forms.
@param {string} formId The ID of the form to show.
@private