anchor.diff:        }
         // Write a new VTable.
         if (vTableTail == null) {
  +        _currentVTable.takeFieldOffsets();
           _prepare(2, _currentVTable.numOfUint16);
           vTableTail = _tail;
           _currentVTable.tail = vTableTail;
  
positive.code:     if (_currentVTable != null) {
        throw new StateError('Inline tables are not supported.');
      }
      _currentVTable = new _VTable();
      _currentTableEndTail = _tail;
    }
  
  
negative.code:  */
  class Builder {
    final int initialSize;
  
    /**
     * The list of field tails, reused by [_VTable] instances.
     */
    final Int32List _reusedFieldTails = Int32List(1024);
  
    /**
     * The list of field offsets, reused by [_VTable] instances.
     */
    final Int32List _reusedFieldOffsets = Int32List(1024);
  
    /**
     * The list of existing VTable(s).
  