Fix bug where a MaskingMediaSource never throws prepare error

We suppressed the direct error throwing ability in <unknown commit>
to avoid throwing errors later in the playlist too early. This
logic got moved to MaskingMediaSource in <unknown commit>, but its
original purpose was no longer needed when the player stopped
calling this method directly in <unknown commit>.

This left a pending bug that any other usage of MaskingMediaSource
(e.g. within AdsMediaSource) no longer forwards source prepare
errors.

Issue: androidx/media#2337
PiperOrigin-RevId: 750537823

RELEASENOTES.md

@@ -9,6 +9,8 @@
         scrubber bar around). The behavior of scrubbing mode can be customized
         with `setScrubbingModeParameters(..)` on `ExoPlayer` and
         `ExoPlayer.Builder`.
+    *   Fix bug where prepare errors in the content of `AdsMediaSource` may be
+        never reported ([#2337](https://github.com/androidx/media/issues/2337)).
 *   Transformer:
     *   Filling an initial gap (added via `addGap()`) with silent audio now
         requires explicitly setting `experimentalSetForceAudioTrack(true)` in

libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/MaskingMediaSource.java

@@ -102,13 +102,6 @@ public final class MaskingMediaSource extends WrappingMediaSource {
     }
   }
 
-  @Override
-  @SuppressWarnings("MissingSuperCall")
-  public void maybeThrowSourceInfoRefreshError() {
-    // Do nothing. Source info refresh errors will be thrown when calling
-    // MaskingMediaPeriod.maybeThrowPrepareError.
-  }
-
   @Override
   public MaskingMediaPeriod createPeriod(
       MediaPeriodId id, Allocator allocator, long startPositionUs) {

libraries/exoplayer/src/test/java/androidx/media3/exoplayer/ExoPlayerTest.java

@@ -16818,6 +16818,27 @@ public final class ExoPlayerTest {
     assertThat(shouldRendererThrowRecoverableError.get()).isFalse();
   }
 
+  @Test
+  public void prepareMaskingMediaSource_withRealSourcePrepareError_reportsPlaybackException()
+      throws Exception {
+    ExoPlayer player = new TestExoPlayerBuilder(context).build();
+    FakeMediaSource realSourceWithPrepareFailure =
+        new FakeMediaSource() {
+          @Override
+          public void maybeThrowSourceInfoRefreshError() throws IOException {
+            throw new IOException();
+          }
+        };
+    realSourceWithPrepareFailure.setAllowPreparation(false);
+    MediaSource maskingMediaSource =
+        new MaskingMediaSource(realSourceWithPrepareFailure, /* useLazyPreparation= */ false);
+    player.setMediaSource(maskingMediaSource);
+
+    player.prepare();
+    // Assert the prepare error is reported.
+    advance(player).untilPlayerError();
+  }
+
   // Internal methods.
 
   private void addWatchAsSystemFeature() {