Move all typecasting code to individual screens.

chrome/browser/chromeos/login/screens/update_screen.cc

 // Copyright (c) 2012 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/screens/update_screen.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/files/file_util.h"
@@ skipping 66 matching lines @@
   return instance_set;
 }
 
 // static
 bool UpdateScreen::HasInstance(UpdateScreen* inst) {
   InstanceSet& instance_set = GetInstanceSet();
   InstanceSet::iterator found = instance_set.find(inst);
   return (found != instance_set.end());
 }
 
+// static
+UpdateScreen* UpdateScreen::Get(ScreenManager* manager) {
+  return static_cast<UpdateScreen*>(
+      manager->GetScreen(WizardController::kUpdateScreenName));
+}
+
 UpdateScreen::UpdateScreen(
     ScreenObserver* screen_observer,
     UpdateScreenActor* actor)
     : WizardScreen(screen_observer),
       state_(STATE_IDLE),
       reboot_check_delay_(0),
       is_checking_for_update_(true),
       is_downloading_update_(false),
       is_ignore_update_deadlines_(false),
       is_shown_(false),
@@ skipping 416 matching lines @@
       GetErrorScreen()->SetErrorState(ErrorScreen::ERROR_STATE_PROXY,
                                       std::string());
       break;
     default:
       NOTREACHED();
       break;
   }
 }
 
 }  // namespace chromeos