text: 'use strict';
  
  if (typeof Promise === 'undefined') {
    // Rejection tracking prevents a common issue where React gets into an
    // inconsistent state due to an error, but it gets swallowed by a Promise,
    // and the user has no idea what causes React's erratic future behavior.
    require('promise/lib/rejection-tracking').enable();
    window.Promise = require('promise/lib/es6-extensions.js');
  }
  
  // In tests, polyfill requestAnimationFrame since jsdom doesn't provide it yet.
  // We don't polyfill it in the browser--this is user's responsibility.
  if (process.env.NODE_ENV === 'test') {
    require('raf').polyfill(global);
  }
  