arc: Start ARC for Public Session users.

components/arc/arc_util.h

Index: components/arc/arc_util.h
diff --git a/components/arc/arc_util.h b/components/arc/arc_util.h
index 7558ac3944d517a869b96bfb36a49f7b1d2dee75..346eff3739c07fc4ff7a549ab3c468b05fd8e7f0 100644
--- a/components/arc/arc_util.h
+++ b/components/arc/arc_util.h
@@ -78,6 +78,13 @@ void SetArcAvailableCommandLineForTesting(base::CommandLine* command_line);
 // should also return true in that case.
 bool IsArcKioskMode();
 
+// Returns true if current user is a robot account user.
+// These are Public Session and ARC Kiosk users.
+// As it can return true only when user is already initialized, it implies
+// that ARC availability was checked before.
+// The check is basically IsArcKioskMode() | IsPublicSessionMode().
+bool IsRobotAccountMode();
+
 // Returns true if ARC is allowed for the given user. Note this should not be
 // used as a signal of whether ARC is allowed alone because it only considers
 // user meta data. e.g. a user could be allowed for ARC but if the user signs in