Fix issue #10461600: KLP API Review: UndoManager

Hide, hide, hide!

Change-Id: Ie04825723d9392a4258e2d738828201ee387f7c6
diff --git a/core/java/android/content/UndoManager.java b/core/java/android/content/UndoManager.java
index 1c2db47..e9ec5a4 100644
--- a/core/java/android/content/UndoManager.java
+++ b/core/java/android/content/UndoManager.java
@@ -50,6 +50,8 @@
  * undo/redo them without needing to impact edits in other objects; while
  * within the larger document, all edits can be seen and the user must
  * undo/redo them as a single stream.</p>
+ *
+ * @hide
  */
 public class UndoManager {
     private final HashMap<String, UndoOwner> mOwners = new HashMap<String, UndoOwner>();