Delete the user key when deleting a user.

Bug: 19706593

(cherry-picked from commit 85e4e818d83dbc65b1e6e3ed9d39c656188acaec)

Change-Id: Icc6d53a99558317b2ec154f931e481ad9fe64aa3
diff --git a/core/java/android/os/storage/StorageManager.java b/core/java/android/os/storage/StorageManager.java
index 5088159..f58ae00 100644
--- a/core/java/android/os/storage/StorageManager.java
+++ b/core/java/android/os/storage/StorageManager.java
@@ -955,6 +955,15 @@
     }
 
     /** {@hide} */
+    public void deleteUserKey(int userHandle) {
+        try {
+            mMountService.deleteUserKey(userHandle);
+        } catch (RemoteException e) {
+            throw e.rethrowAsRuntimeException();
+        }
+    }
+
+    /** {@hide} */
     public static File maybeTranslateEmulatedPathToInternal(File path) {
         final IMountService mountService = IMountService.Stub.asInterface(
                 ServiceManager.getService("mount"));