MediaPlayer subtitle controller: use debug log instead of warning

Don't use warning log for debug message.

Bug 22698299

Change-Id: Ibe3526fffffc9a7bdcda83c02fd745325db1238b

media/java/android/media/MediaPlayer.java

@@ -2292,7 +2292,7 @@ public class MediaPlayer implements SubtitleController.Listener
 
     private void scanInternalSubtitleTracks() {
         if (mSubtitleController == null) {
-            Log.w(TAG, "setSubtitleAnchor in MediaPlayer");
+            Log.d(TAG, "setSubtitleAnchor in MediaPlayer");
             setSubtitleAnchor();
         }