Force encryption migration if the device supports ARC.

chrome/browser/chromeos/login/existing_user_controller.h

 // Copyright (c) 2012 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_EXISTING_USER_CONTROLLER_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_EXISTING_USER_CONTROLLER_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 202 matching lines @@
   // Shows "critical TPM error" screen.
   void ShowTPMError();
 
   // Shows "password changed" dialog.
   void ShowPasswordChangedDialog();
 
   // Creates |login_performer_| if necessary and calls login() on it.
   void PerformLogin(const UserContext& user_context,
                     LoginPerformer::AuthorizationMode auth_mode);
 
+  // calls login() on previously-used |login_performer|.
+  void ContinuePerformLogin(const UserContext& user_context,
+                            LoginPerformer::AuthorizationMode auth_mode);

[xiyuan, 2017/04/06 16:08:59]

nit: maybe we should swap the order of args so that we can bind |auth_mode| on
creating the callback and avoid having to include login_performer.h.

i.e.

void ContinuePerformLogin(LoginPerformer::AuthorizationMode auth_mode,
                          const UserContext& user_context);

And bind the auth mode when creating the callback

base::BindOnce(&ExistingUserController::ContinuePerformLogin,
               weak_factory_.GetWeakPtr(),
               login_performer_->auth_mode());

And callback only needs a UserContext to be invoked.

[fukino, 2017/04/07 02:05:49]

Done.

+
   // Updates the |login_display_| attached to this controller.
   void UpdateLoginDisplay(const user_manager::UserList& users);
 
   // Sends an accessibility alert event to extension listeners.
   void SendAccessibilityAlert(const std::string& alert_text);
 
   // Callback invoked when the keyboard layouts available for a public session
   // have been retrieved. Selects the first layout from the list and continues
   // login.
   void SetPublicSessionKeyboardLayoutAndLogin(
@@ skipping 148 matching lines @@
 
   // Factory of callbacks.
   base::WeakPtrFactory<ExistingUserController> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ExistingUserController);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_EXISTING_USER_CONTROLLER_H_