@Override
  public void setCallback(Callback<T> callback) {
    this.callback = callback;
    call.enqueue(this);
  }
@param request HTTP request to execute.
@param client The client used to execute the request.
@param responseClass Model class to unmarshal JSON body content.
@param fieldNamingPolicy FieldNamingPolicy for unmarshaling JSON.
@param errorTimeOut Number of milliseconds to re-send erroring requests.
@param maxRetries Number of times allowed to re-send erroring requests.
@param exceptionsAllowedToRetry The exceptions to retry.
src/main/java/com/google/maps/internal/OkHttpPendingResult.java