code: function handleCompleteRequestComplete(id, xhr, isError) {
          var promise = pendingCompleteRequests[id],
              domParser = new DOMParser(),
              bucket = options.getBucket(id),
              key = options.getKey(id),
              responseDoc = domParser.parseFromString(xhr.responseText, "application/xml"),
              bucketEls = responseDoc.getElementsByTagName("Bucket"),
              keyEls = responseDoc.getElementsByTagName("Key");
  
          delete pendingCompleteRequests[id];
  
          options.log(qq.format("Complete response status {}, body = {}", xhr.status, xhr.responseText));
  
          // If the base requester has determine this a failure, give up.
          if (isError) {
              options.log(qq.format("Complete Multipart Upload request for {} failed with status {}.", id, xhr.status), "error");
          }
          else {
              // Make sure the correct bucket and key has been specified in the XML response from AWS.
              if (bucketEls.length && keyEls.length) {
                  if (bucketEls[0].textContent !== bucket) {
                      isError = true;
                      options.log(qq.format("Wrong bucket in response to Complete Multipart Upload request for {}.", id), "error");
                  }
  
                  // TODO Compare key name from response w/ expected key name if AWS ever fixes the encoding of key names in this response.
              }
              else {
                  isError = true;
                  options.log(qq.format("Missing bucket and/or key in response to Complete Multipart Upload request for {}.", id), "error");
              }
          }
  
          if (isError) {
              promise.failure("Problem combining the file parts!", xhr);
          }
          else {
              promise.success({}, xhr);
          }
      }
docs: Called by the base ajax requester when the response has been received.  We definitively determine here if the
  "Complete MPU" request has been a success or not.
  
  @param id ID associated with the file.
  @param xhr `XMLHttpRequest` object containing the response, among other things.
  @param isError A boolean indicating success or failure according to the base ajax requester (primarily based on status code).