olly d01093d711 Rollback of dd7b379dc0
*** Original commit ***

DataSource.open() throws if already opened.

Update DataSource implementations to throw an error if open() is called
when the DataSource is already open.

***

PiperOrigin-RevId: 348783425
2020-12-23 22:53:24 +00:00
..
2020-12-23 22:53:24 +00:00