Make Hands-Off Zero-Touch Enrollment compatibile with tests

chrome/browser/chromeos/login/screens/screen_exit_code.h

Index: chrome/browser/chromeos/login/screens/screen_exit_code.h
diff --git a/chrome/browser/chromeos/login/screens/screen_exit_code.h b/chrome/browser/chromeos/login/screens/screen_exit_code.h
index 0f4db28e9c5cf62069ba57edff8c745306f14c70..5b11d2ef78713eb5b20c7874cbdd50734eb58c59 100644
--- a/chrome/browser/chromeos/login/screens/screen_exit_code.h
+++ b/chrome/browser/chromeos/login/screens/screen_exit_code.h
@@ -25,6 +25,10 @@ enum class ScreenExitCode {
   // Connection failed while trying to load a WebPageScreen.
   CONNECTION_FAILED = 2,
   UPDATE_INSTALLED = 3,
+  // Despite the name, this exit code means EITHER that there was no update,
+  // OR that there was an update, but that it was not a "critical" update.
+  // "Critical" updates are those that have a deadline and require the device
+  // to reboot.
   UPDATE_NOUPDATE = 4,
   UPDATE_ERROR_CHECKING_FOR_UPDATE = 5,
   UPDATE_ERROR_UPDATING = 6,