Move all typecasting code to individual screens.

chrome/browser/chromeos/login/supervised/supervised_user_creation_flow.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/chromeos/login/supervised/supervised_user_creation_flow.h"
 
 #include "base/logging.h"
 #include "base/values.h"
 #include "chrome/browser/chromeos/login/supervised/supervised_user_creation_screen.h"
 #include "chrome/browser/chromeos/login/ui/login_display_host_impl.h"
 #include "chrome/browser/chromeos/login/wizard_controller.h"
 #include "chrome/browser/chromeos/profiles/profile_helper.h"
 
 namespace chromeos {
 
 namespace {
 
 SupervisedUserCreationScreen* GetScreen(LoginDisplayHost* host) {
   DCHECK(host);
   DCHECK(host->GetWizardController());
-  DCHECK(host->GetWizardController()->GetSupervisedUserCreationScreen());
-  return host->GetWizardController()->GetSupervisedUserCreationScreen();
+  SupervisedUserCreationScreen* result =
+      SupervisedUserCreationScreen::Get(host->GetWizardController());
+  DCHECK(result);
+  return result;
 }
 
 } // namespace
 
 SupervisedUserCreationFlow::SupervisedUserCreationFlow(
     const std::string& manager_id)
         : ExtendedUserFlow(manager_id),
         token_validated_(false),
         logged_in_(false),
         session_started_(false),
@@ skipping 63 matching lines @@
   if (token_validated_ && logged_in_) {
     if (!session_started_)
       GetScreen(host())->OnManagerFullyAuthenticated(manager_profile_);
     session_started_ = true;
   } else {
     GetScreen(host())->OnManagerCryptohomeAuthenticated();
   }
 }
 
 }  // namespace chromeos