cros: Enable Ext4 migration in ARC kiosk mode.

chrome/browser/chromeos/login/arc_kiosk_controller.h

Index: chrome/browser/chromeos/login/arc_kiosk_controller.h
diff --git a/chrome/browser/chromeos/login/arc_kiosk_controller.h b/chrome/browser/chromeos/login/arc_kiosk_controller.h
index 8408535741e1d974b09fab3bf13f7cf290fc6e86..60814d8075ee00212f8dc580965c9c2751517997 100644
--- a/chrome/browser/chromeos/login/arc_kiosk_controller.h
+++ b/chrome/browser/chromeos/login/arc_kiosk_controller.h
@@ -50,6 +50,8 @@ class ArcKioskController : public LoginPerformer::Delegate,
   void WhiteListCheckFailed(const std::string& email) override;
   void PolicyLoadFailed() override;
   void SetAuthFlowOffline(bool offline) override;
+  void OnOldEncryptionDetected(const UserContext& user_context,
+                               bool has_incomplete_migration) override;
 
   // UserSessionManagerDelegate implementation:
   void OnProfilePrepared(Profile* profile, bool browser_launched) override;