anchor.diff:      if (_currentVTable != null) {
         throw new StateError('Inline tables are not supported.');
       }
  -    _currentVTable = new _VTable();
  +    _currentVTable = new _VTable(_reusedFieldTails, _reusedFieldOffsets);
       _currentTableEndTail = _tail;
     }
   
  
positive.code:  */
  class Builder {
    final int initialSize;
  
    /**
     * The list of existing VTable(s).
  
negative.code:     assert(tail == null);
      assert(existing.tail != null);
      if (tableSize == existing.tableSize &&
          _fieldCount == existing._fieldCount) {
        for (int i = 0; i < _fieldCount; i++) {
          if (_reusedFieldOffsets[i] != existing._fieldOffsets[i]) {
            return false;
          }
        }
  