arc: Show migration success notification on the next sign-in after migration.

chrome/browser/chromeos/arc/arc_migration_guide_notification.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_ARC_ARC_MIGRATION_GUIDE_NOTIFICATION_H_
 #define CHROME_BROWSER_CHROMEOS_ARC_ARC_MIGRATION_GUIDE_NOTIFICATION_H_
 
 class Profile;
 
 namespace arc {
 
 // Shows a notification for guiding the user for file system migration.
 // This is used when an ARC app is launched while ARC is temporaliry disabled
 // due to the file system incompatibility.
 void ShowArcMigrationGuideNotification(Profile* profile);
 
+// Shows a one-time notification when this is the first sign-in after the
+// migration has happend successfully. It records the fact to the pref that no
+// more notification is necessary, either when it showed the notification or
+// when the profile is newly created on the compatible filesystem.
+void ShowArcMigrationSuccessNotificationIfNeeded(Profile* profile);
+
 }  // namespace arc
 
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_ARC_MIGRATION_GUIDE_NOTIFICATION_H_