Fix thumbnail sometimes not set to media session metadata

The thumbnail was not being updated in the media session metadata after it was loaded, since there was no metadata update in that case, only a notification update.

Author: Stypox

app/src/main/java/org/schabi/newpipe/player/mediasession/MediaSessionPlayerUi.java

@@ -1,9 +1,11 @@
 package org.schabi.newpipe.player.mediasession;
 
 import android.content.Intent;
+import android.graphics.Bitmap;
 import android.support.v4.media.session.MediaSessionCompat;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 
 import org.schabi.newpipe.R;
 import org.schabi.newpipe.extractor.stream.StreamInfo;
@@ -60,6 +62,12 @@ public void onMetadataChanged(@NonNull final StreamInfo info) {
         );
     }
 
+    @Override
+    public void onThumbnailLoaded(@Nullable final Bitmap bitmap) {
+        super.onThumbnailLoaded(bitmap);
+        player.getCurrentStreamInfo().ifPresent(this::onMetadataChanged);
+    }
+
     public void handleMediaButtonIntent(final Intent intent) {
         if (mediaSessionManager != null) {
             mediaSessionManager.handleMediaButtonIntent(intent);