Fix indentation and missing javadoc

library/src/main/java/com/google/android/exoplayer2/extractor/mp4/AtomParsers.java

@@ -407,6 +407,7 @@ import java.util.List;
    *
    * @param udtaAtom The udta (user data) atom to decode.
    * @param isQuickTime True for QuickTime media. False otherwise.
+   * @return Parsed metadata, or null.
    */
   public static Metadata parseUdta(Atom.LeafAtom udtaAtom, boolean isQuickTime) {
     if (isQuickTime) {