Fix lint errors in shortform demo app

PiperOrigin-RevId: 629080780

demos/shortform/src/main/java/androidx/media3/demo/shortform/MediaItemDatabase.kt

@@ -32,6 +32,6 @@ class MediaItemDatabase {
 
   fun get(index: Int): MediaItem {
     val uri = mediaUris.get(index.mod(mediaUris.size))
-    return return MediaItem.Builder().setUri(uri).setMediaId(index.toString()).build()
+    return MediaItem.Builder().setUri(uri).setMediaId(index.toString()).build()
   }
 }

demos/shortform/src/main/java/androidx/media3/demo/shortform/PlayerPool.kt

@@ -33,6 +33,7 @@ import java.util.Collections
 import java.util.LinkedList
 import java.util.Queue
 
+@OptIn(UnstableApi::class)
 class PlayerPool(
   private val numberOfPlayers: Int,
   context: Context,
@@ -92,10 +93,10 @@ class PlayerPool(
    *
    * @param keepOngoingPlayer The optional player that should keep playing if not paused.
    */
-  fun pauseAllPlayers(keepOngoingPlayer: Player? = null) {
-    playerMap.values.forEach {
-      if (it != keepOngoingPlayer) {
-        it.pause()
+  private fun pauseAllPlayers(keepOngoingPlayer: Player? = null) {
+    for (player in playerMap.values) {
+      if (player != keepOngoingPlayer) {
+        player.pause()
       }
     }
   }

demos/shortform/src/main/java/androidx/media3/demo/shortform/viewpager/ViewPagerMediaHolder.kt

@@ -49,7 +49,7 @@ class ViewPagerMediaHolder(itemView: View, private val playerPool: PlayerPool) :
     }
   }
 
-  val player: ExoPlayer?
+  private val player: ExoPlayer?
     get() {
       return exoPlayer
     }