When the period has loaded to the end of the source, the `period.getBufferedPositionUs` will be set to `C.TIME_END_OF_SOURCE`, which is a negative value. Thus, the original `continueLoadingPredicate` will never turn to `false`, as the `bufferedPositionUs` is definitely less than the target preload position that is expected to be positive.
In this change, we added `PreloadMediaSource.PreloadControl.onLoadedToTheEndOfSource(PreloadMediaSource)` to indicate that the source has loaded to the end. This allows the `DefaultPreloadManager` and the custom `PreloadMediaSource.PreloadControl` implementations to preload the next source or take other actions.
This bug was not revealed by the the `DefaultPreloadManagerTest` because the related tests were all using the `FakeMediaSource` and only setting the preload target to `STAGE_TIMELINE_REFRESHED`. Thus, the tests for testing the `invalidate()` behaviors were modified to use the real progressive media whenever possible, unless we have to use `FakeMediaSource` to squeeze a chance to do more operations between the preloading of sources to test some special scenarios.
PiperOrigin-RevId: 631776442
1a5f57e9eb