cros: Replace WizardController string constants with OobeScreen values.

chrome/browser/chromeos/login/ui/login_display_host.h

Index: chrome/browser/chromeos/login/ui/login_display_host.h
diff --git a/chrome/browser/chromeos/login/ui/login_display_host.h b/chrome/browser/chromeos/login/ui/login_display_host.h
index 855f42e644097d6aaf5748faecba55cebc34fe29..3395498606272b25dcb5977e9255536cc6788130 100644
--- a/chrome/browser/chromeos/login/ui/login_display_host.h
+++ b/chrome/browser/chromeos/login/ui/login_display_host.h
@@ -10,6 +10,7 @@
 #include "base/callback.h"
 #include "base/callback_list.h"
 #include "chrome/browser/chromeos/customization/customization_document.h"
+#include "chrome/browser/chromeos/login/oobe_screen.h"
 #include "chrome/browser/chromeos/login/ui/login_display.h"
 #include "ui/gfx/native_widget_types.h"
 
@@ -67,8 +68,8 @@ class LoginDisplayHost {
 
   // Starts out-of-box-experience flow or shows other screen handled by
   // Wizard controller i.e. camera, recovery.
-  // One could specify start screen with |first_screen_name|.
-  virtual void StartWizard(const std::string& first_screen_name) = 0;
+  // One could specify start screen with |first_screen|.
+  virtual void StartWizard(OobeScreen first_screen) = 0;
 
   // Returns current WizardController, if it exists.
   // Result should not be stored.