cros: Break BaseScreenHandler into two classes.

chrome/browser/ui/webui/chromeos/login/update_screen_handler.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/update_screen_handler.h"
 
 #include <memory>
 
 #include "base/values.h"
 #include "chrome/browser/chromeos/login/oobe_screen.h"
 #include "chrome/browser/chromeos/login/screens/update_screen.h"
 #include "chrome/grit/chromium_strings.h"
 #include "chrome/grit/generated_resources.h"
 #include "components/login/localized_values_builder.h"
 
 namespace {
 
 const char kJsScreenPath[] = "login.UpdateScreen";
 
 }  // namespace
 
 namespace chromeos {
 
-UpdateScreenHandler::UpdateScreenHandler() {
+UpdateScreenHandler::UpdateScreenHandler() : BaseScreenHandler(kScreenId) {
   set_call_js_prefix(kJsScreenPath);
 }
 
 UpdateScreenHandler::~UpdateScreenHandler() {
   if (screen_)
     screen_->OnViewDestroyed(this);
 }
 
 void UpdateScreenHandler::DeclareLocalizedValues(
     ::login::LocalizedValuesBuilder* builder) {
@@ skipping 28 matching lines @@
     Show();
     show_on_init_ = false;
   }
 }
 
 void UpdateScreenHandler::Show() {
   if (!page_is_ready()) {
     show_on_init_ = true;
     return;
   }
-  ShowScreen(OobeScreen::SCREEN_OOBE_UPDATE);
+  ShowScreen(kScreenId);
 }
 
 void UpdateScreenHandler::Hide() {
 }
 
 void UpdateScreenHandler::Bind(UpdateScreen* screen) {
   screen_ = screen;
   BaseScreenHandler::SetBaseScreen(screen_);
 }
 
 void UpdateScreenHandler::Unbind() {
   screen_ = nullptr;
   BaseScreenHandler::SetBaseScreen(nullptr);
 }
 
 }  // namespace chromeos