HLS: Fix issue where a live event doesn't transition to STATE_ENDED

The problem occurs when the primary media playlist URL switches
from one whose latest snapshot has not yet got the ended tag, to
one whose latest snapshot already has the ended tag. In this case:

- We trigger a redundant load of the ended playlist.
- When the redundant load completes,
  MediaPlaylistBundle.processLoadedPlaylist detects that the
  playlist is unchanged from the one it already has, and so
  doesn't call onPlaylistUpdated.
- PrimaryPlaylistListener.onPrimaryPlaylistRefreshed is never
  called with the new primary. Hence the externally visible primary
  is still the one that hasn't ended. HlsMediaSource therefore thinks
  the event hasn't ended, which in turn prevents the player from
  transitioning to the ended state.

This commit detects when the new primary already has the ended tag.
In this case, we call onPrimaryPlaylistRefreshed directly and remove
the unnecessary playlist load.

Issue: #9067
#minor-release
PiperOrigin-RevId: 380680532

RELEASENOTES.md

@@ -65,6 +65,9 @@
         ([#4083](https://github.com/google/ExoPlayer/issues/4083)). Such content
         is malformed and should be re-encoded.
 *   HLS:
+    *   Fix issue where playback of a live event could become stuck rather than
+        transitioning to `STATE_ENDED` when the event ends
+        ([#9067](https://github.com/google/ExoPlayer/issues/9067)).
     *   Fix issue where a new initialization segment, as specified by an
         `EXT-X-MAP` tag in a media playlist, would not be loaded when
         encountered during playback

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/DefaultHlsPlaylistTracker.java

@@ -339,9 +339,16 @@ public final class DefaultHlsPlaylistTracker
       return;
     }
     primaryMediaPlaylistUrl = url;
-    playlistBundles
+    MediaPlaylistBundle newPrimaryBundle = playlistBundles.get(primaryMediaPlaylistUrl);
-        .get(primaryMediaPlaylistUrl)
+    @Nullable HlsMediaPlaylist newPrimarySnapshot = newPrimaryBundle.playlistSnapshot;
-        .loadPlaylistInternal(getRequestUriForPrimaryChange(url));
+    if (newPrimarySnapshot != null && newPrimarySnapshot.hasEndTag) {
+      primaryMediaPlaylistSnapshot = newPrimarySnapshot;
+      primaryPlaylistListener.onPrimaryPlaylistRefreshed(newPrimarySnapshot);
+    } else {
+      // The snapshot for the new primary media playlist URL may be stale. Defer updating the
+      // primary snapshot until after we've refreshed it.
+      newPrimaryBundle.loadPlaylistInternal(getRequestUriForPrimaryChange(url));
+    }
   }
 
   private Uri getRequestUriForPrimaryChange(Uri newPrimaryPlaylistUri) {