Check the available storage size before starting encryption migration.

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 "base/callback_forward.h"
 #include "chrome/browser/chromeos/login/screens/base_screen.h"
 #include "chrome/browser/chromeos/login/screens/encryption_migration_screen_view.h"
@@ skipping 23 matching lines @@
   // Sets the UserContext for a user whose cryptohome should be migrated.
   void SetUserContext(const UserContext& user_context);
 
   // Sets whether the migration process should resume the previous one or not.
   void SetShouldResume(bool should_resume);
 
   // 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);
 
+  // Setup the initial view in the migration UI.
+  // This should be called after other state like UserContext, etc... are set.
+  void SetupInitialView();
+
  private:
   EncryptionMigrationScreenView* view_;
 
   DISALLOW_COPY_AND_ASSIGN(EncryptionMigrationScreen);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_ENCRYPTION_MIGRATION_SCREEN_H_