constructor(
      onIdpClick, providerConfigs, opt_tosCallback, opt_privacyPolicyCallback,
      domHelper = undefined) {
    super(
        page.providerSignIn,
        {providerConfigs: providerConfigs}, domHelper, 'providerSignIn', {
          tosCallback: opt_tosCallback,
          privacyPolicyCallback: opt_privacyPolicyCallback,
        });
    this.onIdpClick_ = onIdpClick;
  }
@param {function(string)} onIdpClick Callback to invoke when the user
    clicks one IdP button.
@param {!Array<!Object>} providerConfigs The provider configs of the IdPs
    to display.
@param {?function()=} opt_tosCallback Callback to invoke when the ToS link
    is clicked.
@param {?function()=} opt_privacyPolicyCallback Callback to invoke when
    the Privacy Policy link is clicked.
@param {?DomHelper=} domHelper Optional DOM helper.