cros: Replace WizardController string constants with OobeScreen values.

chrome/browser/ui/webui/chromeos/login/oobe_ui.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/ui/webui/chromeos/login/oobe_ui.h"
 
 #include <stddef.h>
 
 #include <memory>
 
@@ skipping 578 matching lines @@
 
 
 void OobeUI::AddObserver(Observer* observer) {
   observer_list_.AddObserver(observer);
 }
 
 void OobeUI::RemoveObserver(Observer* observer) {
   observer_list_.RemoveObserver(observer);
 }
 
-void OobeUI::OnCurrentScreenChanged(const std::string& screen) {
+void OobeUI::OnCurrentScreenChanged(OobeScreen new_screen) {
   previous_screen_ = current_screen_;
-  OobeScreen new_screen = GetOobeScreenFromName(screen);
 
   const bool should_dim =
       std::find(std::begin(kDimOverlayScreenIds),
                 std::end(kDimOverlayScreenIds),
                 new_screen) != std::end(kDimOverlayScreenIds);
   if (!chrome::IsRunningInMash()) {
     if (!screen_dimmer_) {
       screen_dimmer_ = base::MakeUnique<ash::ScreenDimmer>(
           ash::ScreenDimmer::Container::LOCK_SCREEN);
     }
     screen_dimmer_->set_at_bottom(true);
     screen_dimmer_->SetDimming(should_dim);
   } else {
     // TODO: Ash needs to expose screen dimming api. See
     // http://crbug.com/646034.
     NOTIMPLEMENTED();
   }
 
   current_screen_ = new_screen;
   for (Observer& observer : observer_list_)
     observer.OnCurrentScreenChanged(current_screen_, new_screen);
 }
 
 }  // namespace chromeos