Fix HlsPlaybackTest flakiness

The new test introduced in 45bd5c6 is flaky because we only
wait until the media is fully buffered. However, we can't fully
control how much of this data is initially read by the Robolectric
codec and thus the output dump files (containing these codec
interactions) are flaky.

This can be fixed by fully playing the media once and then seeking
back instead.

#minor-release

PiperOrigin-RevId: 603324068
(cherry picked from commit e3e57c9)

Author: tonihei

libraries/exoplayer_hls/src/test/java/androidx/media3/exoplayer/hls/e2etest/HlsPlaybackTest.java

@@ -22,6 +22,7 @@
 import androidx.media3.common.MediaItem;
 import androidx.media3.common.Player;
 import androidx.media3.datasource.DefaultDataSource;
+import androidx.media3.exoplayer.DefaultLoadControl;
 import androidx.media3.exoplayer.ExoPlayer;
 import androidx.media3.exoplayer.SeekParameters;
 import androidx.media3.exoplayer.hls.HlsMediaSource;
@@ -167,14 +168,19 @@ public void multiSegment_withSeekToPrevSyncFrame_startsRenderingAtBeginningOfSeg
                 new HlsMediaSource.Factory(new DefaultDataSource.Factory(applicationContext))
                     .experimentalParseSubtitlesDuringExtraction(true))
             .setClock(new FakeClock(/* isAutoAdvancing= */ true))
+            .setLoadControl(
+                new DefaultLoadControl.Builder()
+                    .setBackBuffer(
+                        /* backBufferDurationMs= */ 10000, /* retainBackBufferFromKeyframe= */ true)
+                    .build())
             .build();
-    // Prepare media fully to ensure we have all the segment data available.
     player.setVideoSurface(new Surface(new SurfaceTexture(/* texName= */ 1)));
     PlaybackOutput playbackOutput = PlaybackOutput.register(player, capturingRenderersFactory);
+    // Play media fully (with back buffer) to ensure we have all the segment data available.
     player.setMediaItem(MediaItem.fromUri("asset:///media/hls/multi-segment/playlist.m3u8"));
     player.prepare();
-    TestPlayerRunHelper.runUntilIsLoading(player, true);
-    TestPlayerRunHelper.runUntilIsLoading(player, false);
+    player.play();
+    TestPlayerRunHelper.runUntilPlaybackState(player, Player.STATE_ENDED);
 
     // Seek to beginning of second segment (at 500ms according to playlist)
     player.setSeekParameters(SeekParameters.PREVIOUS_SYNC);