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

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

Index: chrome/browser/chromeos/login/screens/encryption_migration_screen_view.h
diff --git a/chrome/browser/chromeos/login/screens/encryption_migration_screen_view.h b/chrome/browser/chromeos/login/screens/encryption_migration_screen_view.h
new file mode 100644
index 0000000000000000000000000000000000000000..d920b85bb622c50fcfcbf92a2014891b58e076b8
--- /dev/null
+++ b/chrome/browser/chromeos/login/screens/encryption_migration_screen_view.h
@@ -0,0 +1,38 @@
+// 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_VIEW_H_
+#define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_ENCRYPTION_MIGRATION_SCREEN_VIEW_H_
+
+#include "chrome/browser/chromeos/login/oobe_screen.h"
+
+namespace chromeos {
+
+class EncryptionMigrationScreenView {
+ public:
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+
+    // Called when screen is exited.
+    virtual void OnExit() = 0;
+
+    // This method is called, when view is being destroyed. Note, if Delegate is
+    // destroyed earlier then it has to call SetDelegate(NULL).
+    virtual void OnViewDestroyed(EncryptionMigrationScreenView* view) = 0;
+  };
+
+  constexpr static OobeScreen kScreenId =
+      OobeScreen::SCREEN_ENCRYPTION_MIGRATION;
+
+  virtual ~EncryptionMigrationScreenView() {}
+
+  virtual void Show() = 0;
+  virtual void Hide() = 0;
+  virtual void SetDelegate(Delegate* delegate) = 0;
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_ENCRYPTION_MIGRATION_SCREEN_VIEW_H_