Add TODOs for registerReceiver calls without flag

PiperOrigin-RevId: 461165173
(cherry picked from commit 9271572e)

libraries/session/src/main/java/androidx/media3/session/MediaSessionImpl.java

@@ -210,6 +210,7 @@ import org.checkerframework.checker.initialization.qual.Initialized;
       broadcastReceiver = new MediaButtonReceiver();
       IntentFilter filter = new IntentFilter(Intent.ACTION_MEDIA_BUTTON);
       filter.addDataScheme(castNonNull(sessionUri.getScheme()));
+      // TODO(b/197817693): Explicitly indicate whether the receiver should be exported.
       context.registerReceiver(broadcastReceiver, filter);
     } else {
       // Has MediaSessionService to revive playback after it's dead.

libraries/ui/src/main/java/androidx/media3/ui/PlayerNotificationManager.java

@@ -1164,6 +1164,7 @@ public class PlayerNotificationManager {
     Notification notification = builder.build();
     notificationManager.notify(notificationId, notification);
     if (!isNotificationStarted) {
+      // TODO(b/197817693): Explicitly indicate whether the receiver should be exported.
       context.registerReceiver(notificationBroadcastReceiver, intentFilter);
     }
     if (notificationListener != null) {