Rewrite simple uses of base::ListValue::Append(base::Value*) on CrOS.

components/user_manager/user_manager_base.cc

Index: components/user_manager/user_manager_base.cc
diff --git a/components/user_manager/user_manager_base.cc b/components/user_manager/user_manager_base.cc
index 8cd5d50b9c150a4d705c8c92d5ce25fb12fdb9e8..5c9604083030ab880c09e971a6494611894e3fe0 100644
--- a/components/user_manager/user_manager_base.cc
+++ b/components/user_manager/user_manager_base.cc
@@ -966,7 +966,7 @@ User* UserManagerBase::RemoveRegularOrSupervisedUserFromList(
     } else {
       if ((*it)->HasGaiaAccount() || (*it)->IsSupervised()) {
         const std::string user_email = (*it)->email();
-        prefs_users_update->Append(new base::StringValue(user_email));
+        prefs_users_update->AppendString(user_email);
       }
       ++it;
     }