chrome/renderer/resources/extensions/identity_custom_bindings.js

// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Custom binding for the Identity API.

apiBridge.registerCustomHook(function(binding, id, contextType) {
  const apiFunctions = binding.apiFunctions;

  apiFunctions.setHandleRequest('getRedirectURL', function(path) {
    if (path === null || path === undefined) {
      path = '/';
    } else {
      path = String(path);
    }
    if (path[0] !== '/') {
      path = '/' + path;
    }
    return 'https://' + id + '.chromiumapp.org' + path;
  });
});