Fix bug where SilenceMediaSource#getTag was always returning null.

SilenceMediaSource never overloaded MediaSource#getTag, and default behavior is to return null.

PiperOrigin-RevId: 314779832

RELEASENOTES.md

@@ -3,6 +3,7 @@
 ### dev-v2 (not yet released)
 
 *   Core library:
+    *   Implement getTag for SilenceMediaSource.
     *   Add `Player.getTrackSelector` to access track selector from UI module.
     *   Added `TextComponent.getCurrentCues` because the current cues are no
         longer forwarded to a new `TextOutput` in `SimpleExoPlayer`

library/core/src/main/java/com/google/android/exoplayer2/source/SilenceMediaSource.java

@@ -151,6 +151,12 @@ public final class SilenceMediaSource extends BaseMediaSource {
     return mediaItem;
   }
 
+  @Nullable
+  @Override
+  public Object getTag() {
+    return Assertions.checkNotNull(mediaItem.playbackProperties).tag;
+  }
+
   @Override
   protected void releaseSourceInternal() {}
 

library/core/src/test/java/com/google/android/exoplayer2/source/SilenceMediaSourceTest.java

@@ -53,6 +53,16 @@ public class SilenceMediaSourceTest {
   }
 
   @Test
+  public void builderSetTag_setsTagOfMediaSource() {
+    Object tag = new Object();
+
+    SilenceMediaSource mediaSource =
+        new SilenceMediaSource.Factory().setTag(tag).setDurationUs(1_000_000).createMediaSource();
+
+    assertThat(mediaSource.getMediaItem().playbackProperties.tag).isEqualTo(tag);
+  }
+
+  @Test
   public void builder_setDurationUsNotCalled_throwsIllegalStateException() {
     assertThrows(IllegalStateException.class, new SilenceMediaSource.Factory()::createMediaSource);
   }