Add a datatype for supervised user whitelists.

sync/internal_api/public/base/model_type.h

Index: sync/internal_api/public/base/model_type.h
diff --git a/sync/internal_api/public/base/model_type.h b/sync/internal_api/public/base/model_type.h
index 511f66b25d8b8d88cc15ff1e5bb11934fd3785f4..783d0c4097a9ab034b02253a88ae79ca5626e7f0 100644
--- a/sync/internal_api/public/base/model_type.h
+++ b/sync/internal_api/public/base/model_type.h
@@ -114,6 +114,9 @@ enum ModelType {
   // WiFi credentials. Each item contains the information for connecting to one
   // WiFi network. This includes, e.g., network name and password.
   WIFI_CREDENTIALS,
+  // Supervised user whitelists. Each item contains the same information as for
+  // an extension. The data type is separate to allow syncing only whitelists.
+  SUPERVISED_USER_WHITELISTS,
 
   // ---- Proxy types ----
   // Proxy types are excluded from the sync protocol, but are still considered