enable devel xhprof for 8.x

settings.php

if (!drupal_valid_test_ua()) {
  $path = '/var/www';
  $conf['devel.settings']['xhprof_enabled'] = 1;
  $conf['devel.settings']['xhprof_directory'] = '/var/www';
  $conf['devel.settings']['xhprof_url'] = 'http://localhost/xhprof_html';
  include_once $path . '/xhprof_lib/utils/xhprof_lib.php';
  include_once $path . '/xhprof_lib/utils/xhprof_runs.php';
  xhprof_enable(XHPROF_FLAGS_CPU + XHPROF_FLAGS_MEMORY);
  drupal_register_shutdown_function('devel_shutdown');
}