Allow apps with CREATE_USERS permission to create demo users.

Bug: 31092477
Test: adb shell am create-user --ephemeral --demo <user-name>
Change-Id: Ia08a50ec4371466c62cdc9f5391e298a666b5081
diff --git a/services/core/java/com/android/server/pm/UserManagerService.java b/services/core/java/com/android/server/pm/UserManagerService.java
index c9ad49a..af055da 100644
--- a/services/core/java/com/android/server/pm/UserManagerService.java
+++ b/services/core/java/com/android/server/pm/UserManagerService.java
@@ -180,7 +180,8 @@
             UserInfo.FLAG_MANAGED_PROFILE
             | UserInfo.FLAG_EPHEMERAL
             | UserInfo.FLAG_RESTRICTED
-            | UserInfo.FLAG_GUEST;
+            | UserInfo.FLAG_GUEST
+            | UserInfo.FLAG_DEMO;
 
     private static final int MIN_USER_ID = 10;
     // We need to keep process uid within Integer.MAX_VALUE.