tonihei 6a491e1294 Verify MediaSources passed to set/addMediaSources are non-null.
Even though they are annotated as non-null, Java users can pass in null values.
So we should verify the input to fail fast.

PiperOrigin-RevId: 306425487
2020-04-15 17:42:18 +01:00
..
2020-04-08 21:48:08 +01:00