onCancel = function() {
    component.dispose();
    // On cancel return to widget start page.
    firebaseui.auth.widget.handler.common.handleSignInStart(app, container);
  }
Handles password sign up.

@param {firebaseui.auth.AuthUI} app The current Firebase UI instance whose
    configuration is used.
@param {Element} container The container DOM element.
@param {string=} opt_email The email address of the account.
@param {string=} opt_name The display name of the account.
@param {boolean=} opt_disableCancel Whether to disable the cancel link.
@param {boolean=} opt_displayFullTosPpMessage Whether to display the full
    message of Term of Service and Privacy Policy.