Unhide MediaPlayer.setNextMediaPlayer

The Music apps are unbundled, so this needs to be unhidden for them to use it.

Change-Id: I24330a2d6cfa2f5fb5f9c282d28f5431b6165095

Author: marcone

api/current.txt

@@ -10891,6 +10891,7 @@ package android.media {
     method public void setDataSource(java.io.FileDescriptor, long, long) throws java.io.IOException, java.lang.IllegalArgumentException, java.lang.IllegalStateException;
     method public void setDisplay(android.view.SurfaceHolder);
     method public void setLooping(boolean);
+    method public void setNextMediaPlayer(android.media.MediaPlayer);
     method public void setOnBufferingUpdateListener(android.media.MediaPlayer.OnBufferingUpdateListener);
     method public void setOnCompletionListener(android.media.MediaPlayer.OnCompletionListener);
     method public void setOnErrorListener(android.media.MediaPlayer.OnErrorListener);

media/java/android/media/MediaPlayer.java

@@ -1170,7 +1170,6 @@ public int setMetadataFilter(Set<Integer> allow, Set<Integer> block) {
      *
      * @param next the player to start after this one completes playback.
      *
-     * @hide
      */
     public native void setNextMediaPlayer(MediaPlayer next);