MediaSessionManager: Fix error in listener's nullable annotation

Bug: 138648566
Test: Build
Change-Id: I7e7d01ab405eb1d53352587486cd71cc4453059f
diff --git a/api/system-current.txt b/api/system-current.txt
index 4ab8d58..f77d74d 100755
--- a/api/system-current.txt
+++ b/api/system-current.txt
@@ -4311,7 +4311,7 @@
   }
 
   public static interface MediaSessionManager.OnMediaKeyEventDispatchedListener {
-    method public default void onMediaKeyEventDispatched(@NonNull android.view.KeyEvent, @NonNull String, @NonNull android.media.session.MediaSession.Token);
+    method public default void onMediaKeyEventDispatched(@NonNull android.view.KeyEvent, @NonNull String, @Nullable android.media.session.MediaSession.Token);
   }
 
   public static interface MediaSessionManager.OnMediaKeyEventSessionChangedListener {
diff --git a/media/java/android/media/session/MediaSessionManager.java b/media/java/android/media/session/MediaSessionManager.java
index aff7257..aece39d 100644
--- a/media/java/android/media/session/MediaSessionManager.java
+++ b/media/java/android/media/session/MediaSessionManager.java
@@ -940,16 +940,15 @@
         /**
          * Called when a media key event is dispatched through the media session service. The
          * session token can be {@link null} if the framework has sent the media key event to the
-         * media button receiver to revive the media app's playback.
-         *
-         * the session is dead when , but the framework sent
+         * media button receiver to revive the media app's playback after the corresponding session
+         * is released.
          *
          * @param event Dispatched media key event.
          * @param packageName Package
          * @param sessionToken The media session's token. Can be {@code null}.
          */
         default void onMediaKeyEventDispatched(@NonNull KeyEvent event, @NonNull String packageName,
-                @NonNull MediaSession.Token sessionToken) { }
+                @Nullable MediaSession.Token sessionToken) { }
     }
 
     /**