See the following code in HeapHashTable::ExpandBuffer.

  ValueType* original_table = table_;

  ValueType* temporary_table = AllocateTable(old_table_size);
  for (unsigned i = 0; i < old_table_size; i++) {
    if (&table_[i] == entry)
      new_entry = &temporary_table[i];
    if (IsEmptyOrDeletedBucket(table_[i])) {
      ...
    } else {
      Mover<ValueType, Allocator,
            Traits::template NeedsToForbidGCOnMove<>::value>::
          Move(std::move(table_[i]), temporary_table[i]);
    }
  }
  table_ = temporary_table;

  if (Traits::kEmptyValueIsZero) {
    memset(original_table, 0, new_table_size * sizeof(ValueType));
  } else {
    for (unsigned i = 0; i < new_table_size; i++)
      InitializeBucket(original_table[i]);
  }

The function clears |original_table_| without calling destructors of each valid element.