Force encryption migration if the device supports ARC.

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

Index: chrome/browser/chromeos/login/screens/encryption_migration_screen.h
diff --git a/chrome/browser/chromeos/login/screens/encryption_migration_screen.h b/chrome/browser/chromeos/login/screens/encryption_migration_screen.h
index 5764afe5c51fc53ff5bcc9b2ef3cbaf401c0fcd6..4ba1e30d0e69909c16e8a593c02a337b5e8fa40a 100644
--- a/chrome/browser/chromeos/login/screens/encryption_migration_screen.h
+++ b/chrome/browser/chromeos/login/screens/encryption_migration_screen.h
@@ -5,6 +5,7 @@
 #ifndef CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_ENCRYPTION_MIGRATION_SCREEN_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_ENCRYPTION_MIGRATION_SCREEN_H_
 
+#include "base/callback_forward.h"
 #include "chrome/browser/chromeos/login/screens/base_screen.h"
 #include "chrome/browser/chromeos/login/screens/encryption_migration_screen_view.h"
 
@@ -16,6 +17,8 @@ class EncryptionMigrationScreen
     : public BaseScreen,
       public EncryptionMigrationScreenView::Delegate {
  public:
+  using ContinueLoginCallback = base::OnceCallback<void(const UserContext&)>;
+
   EncryptionMigrationScreen(BaseScreenDelegate* base_screen_delegate,
                             EncryptionMigrationScreenView* view);
   ~EncryptionMigrationScreen() override;
@@ -31,6 +34,10 @@ class EncryptionMigrationScreen
   // Sets the UserContext for a user whose cryptohome should be migrated.
   void SetUserContext(const UserContext& user_context);
 
+  // Sets a callback, which should be called when the user want to log in to the
+  // session from the migration UI.
+  void SetContinueLoginCallback(ContinueLoginCallback callback);
+
  private:
   EncryptionMigrationScreenView* view_;