code: long storeSpaceForAdd() {
          return ConcurrentSubList.maximumSerializedSize() // List header
                 + 3 * ConcurrentSubList.Link.maximumSerializedSize() // Current,Previous,Next links  
                 + 4 * owningToken.objectStore.getAddSpaceOverhead() // Store overhead for all of the above.
                 + storeSpaceForRemove(); // In case we backoutTheAdd.
      }
docs: The space we reserve in the ObjectStore before we begin an add operation.
  
  @return long a worst case estimate of the ObjectStore space needed to add an entry
  to this list.