Add a screen to migrate filesystem encryption from eCryptfs to ext4 crypto.

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

+// Copyright 2017 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_ENCRYPTION_MIGRATION_SCREEN_H_
+#define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_ENCRYPTION_MIGRATION_SCREEN_H_
+
+#include "chrome/browser/chromeos/login/screens/base_screen.h"
+#include "chrome/browser/chromeos/login/screens/encryption_migration_screen_view.h"
+
+namespace chromeos {
+
+class EncryptionMigrationScreen
+    : public BaseScreen,
+      public EncryptionMigrationScreenView::Delegate {
+ public:
+  EncryptionMigrationScreen(BaseScreenDelegate* base_screen_delegate,
+                            EncryptionMigrationScreenView* view);
+  ~EncryptionMigrationScreen() override;
+
+  // BaseScreen:
+  void Show() override;
+  void Hide() override;
+
+  // EncryptionMigrationScreenView::Delegate:
+  void OnExit() override;
+  void OnViewDestroyed(EncryptionMigrationScreenView* view) override;
+
+ private:
+  EncryptionMigrationScreenView* view_;
+
+  DISALLOW_COPY_AND_ASSIGN(EncryptionMigrationScreen);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_ENCRYPTION_MIGRATION_SCREEN_H_