code: function _makeSimulatedNetworkRequest(getValue) {
    const durationMs = 400;
    return new Promise(function (resolve, reject) {
      setTimeout(function () {
        if (isNetworkFailure()) {
          reject(new Error('Network failure'));
        } else {
          getValue(resolve, reject);
        }
      }, durationMs);
    });
  }
docs: Helper for the other functions in this file.
  Simulates a short delay and then returns a provided value or failure.
  This is just a dummy example. Normally we'd make a HTTP request,
  see http://facebook.github.io/react-native/docs/network.html