anchor.diff:              }
           }
   
  +        private void CheckoutPoll(Action<List<string>, string> callback) {
  +            PollTillReady(
  +                checkout => {
  +                    return checkout.ready();
  +                },
  +                callback
  +            );
  +        }
  +
           private void OnDeleteLineItem(string lineItemId) {
               DeletedLineItems.Add(lineItemId);
           }
  
positive.code: 
                          UpdateCheckout(checkout);
  
                          if (CurrentCheckout.ready()) {
                              callback(null, null);
                          } else {
                              #if !SHOPIFY_MONO_UNIT_TEST
                                  UnityTimeout.Start(POLL_DELAY_SECONDS, () => {
                                      CheckoutPoll(callback);    
                                  });
                              #else
                                  CheckoutPoll(callback);
                              #endif
                          }
                      }
  
negative.code:             _LineItems = new CartLineItems(OnDeleteLineItem);
          }
  
          public delegate bool IsReadyGivenCheckout(Checkout checkout);
          public delegate void GetWebCheckoutLinkSuccess(string url);
          public delegate void GetWebCheckoutLinkFailure(List<string> graphQLErrors, string httpError);
  
  