Retail mode flag and some clients for it

Bug: 27280140
Change-Id: Ide33e941b9c71eb925b5977d0b0d62198537ca14
diff --git a/core/java/android/provider/Settings.java b/core/java/android/provider/Settings.java
index f04b2d4..a5c2500 100755
--- a/core/java/android/provider/Settings.java
+++ b/core/java/android/provider/Settings.java
@@ -8538,6 +8538,15 @@
         public static final String SAFE_BOOT_DISALLOWED = "safe_boot_disallowed";
 
         /**
+         * Whether this device is currently in retail demo mode. If true, device
+         * usage is severely limited.
+         * <p>
+         * Type: int (0 for false, 1 for true)
+         * @hide
+         */
+        public static final String DEVICE_DEMO_MODE = "device_demo_mode";
+
+        /**
          * Settings to backup. This is here so that it's in the same place as the settings
          * keys and easy to update.
          *