code: function tryToMergeEntryInList(list, entry) {
      if (list.has(entry.url) === false) {
          return false;
      }
      // Get the entry
      var loadingEntry = list.get(entry.url);
  
      // Pass new callbacks to the entry - will be triggered all requests
      loadingEntry.callbacks.error.push(entry.callbacks.error[0]);
      loadingEntry.callbacks.success.push(entry.callbacks.success[0]);
  
      // Copy the executing task
      entry.task = loadingEntry.task;
      return true;
  }
docs: Tries to merge success/error callbacks for existing entry
  in given list. Returns true if merged. Used for multiple callback calls
  for same entry
  
  @param {EntryList} list
  @param {QueueEntry} entry
  @return {boolean}