olly 47601980d9 Use DownloadAction.id properly
- Fix ID being dropped when DownloadAction is serialized and
  de-serialized as it's passed to DownloadService
- Properly set DownloadAction.id when building an action from
  a DownloadState
- Make ID a required constructor argument. Else it's too easy
  to not propagate it by accident.

PiperOrigin-RevId: 242457831
2019-04-13 01:34:07 +01:00
..
2019-04-13 01:34:07 +01:00