Revert of Fold UpdateModel into UpdateScreen.

chrome/browser/chromeos/login/screens/update_model.h

Index: chrome/browser/chromeos/login/screens/update_model.h
diff --git a/chrome/browser/chromeos/login/screens/update_model.h b/chrome/browser/chromeos/login/screens/update_model.h
new file mode 100644
index 0000000000000000000000000000000000000000..2a8a7ed21ea0b06c822aeffb3da2280877286729
--- /dev/null
+++ b/chrome/browser/chromeos/login/screens/update_model.h
@@ -0,0 +1,37 @@
+// Copyright 2015 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_UPDATE_MODEL_H_
+#define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_UPDATE_MODEL_H_
+
+#include "chrome/browser/chromeos/login/screens/base_screen.h"
+
+namespace chromeos {
+
+class BaseScreenDelegate;
+class UpdateView;
+
+class UpdateModel : public BaseScreen {
+ public:
+  static const char kUserActionCancelUpdateShortcut[];
+  static const char kContextKeyEstimatedTimeLeftSec[];
+  static const char kContextKeyShowEstimatedTimeLeft[];
+  static const char kContextKeyUpdateMessage[];
+  static const char kContextKeyShowCurtain[];
+  static const char kContextKeyShowProgressMessage[];
+  static const char kContextKeyProgress[];
+  static const char kContextKeyProgressMessage[];
+  static const char kContextKeyCancelUpdateShortcutEnabled[];
+
+  explicit UpdateModel(BaseScreenDelegate* base_screen_delegate);
+  ~UpdateModel() override;
+
+  // This method is called, when view is being destroyed. Note, if model
+  // is destroyed earlier then it has to call Unbind().
+  virtual void OnViewDestroyed(UpdateView* view) = 0;
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_UPDATE_MODEL_H_