Convert //chrome/browser/chromeos from scoped_ptr to std::unique_ptr

chrome/browser/chromeos/login/users/mock_user_manager.h

Index: chrome/browser/chromeos/login/users/mock_user_manager.h
diff --git a/chrome/browser/chromeos/login/users/mock_user_manager.h b/chrome/browser/chromeos/login/users/mock_user_manager.h
index 8791db30f7b4d4d384247ce3d8599171f8a922fc..8f86804ab71fb6aa19d5fa71f96c5c71e8f1f52d 100644
--- a/chrome/browser/chromeos/login/users/mock_user_manager.h
+++ b/chrome/browser/chromeos/login/users/mock_user_manager.h
@@ -168,9 +168,9 @@ class MockUserManager : public ChromeUserManager {
   // MockUserManager become invalid.
   void ClearUserList();
 
-  scoped_ptr<UserFlow> user_flow_;
-  scoped_ptr<MockUserImageManager> user_image_manager_;
-  scoped_ptr<FakeSupervisedUserManager> supervised_user_manager_;
+  std::unique_ptr<UserFlow> user_flow_;
+  std::unique_ptr<MockUserImageManager> user_image_manager_;
+  std::unique_ptr<FakeSupervisedUserManager> supervised_user_manager_;
   user_manager::UserList user_list_;
   // TODO (alemate): remove temporary_owner_account_id_ as soon as
   // User::GetAccountId will