In many cases we're passing a 'custom' DataSource.Factory where it's not
relevant for the respective dev guide section.
#minor-release
PiperOrigin-RevId: 450374171
This more closely matches the pattern we have for all implementations
except DefaultMediaSourceFactory (e.g. ProgressiveMediaSource.Factory)
and other factory interfaces like (Http)DataSource.Factory.
PiperOrigin-RevId: 417826803