Chromad: Add authentication flow

chromeos/login/auth/user_context.h

Index: chromeos/login/auth/user_context.h
diff --git a/chromeos/login/auth/user_context.h b/chromeos/login/auth/user_context.h
index 16d217556347d0f0d710cb9fc6abf1b0b58e2946..db4883e3c21a17d742361609ace1eea2c41c1c7b 100644
--- a/chromeos/login/auth/user_context.h
+++ b/chromeos/login/auth/user_context.h
@@ -34,7 +34,9 @@ class CHROMEOS_EXPORT UserContext {
     // Offline authentication using and Easy unlock device (e.g. a phone).
     AUTH_FLOW_EASY_UNLOCK,
     // Easy bootstrap flow.
-    AUTH_FLOW_EASY_BOOTSTRAP
+    AUTH_FLOW_EASY_BOOTSTRAP,
+    // Authentication against Active Directory server.
+    AUTH_FLOW_AD
   };
 
   UserContext();