chrome/android/java/res/xml/theme_preferences.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2019 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. -->

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    <org.chromium.chrome.browser.night_mode.settings.RadioButtonGroupThemePreference
        android:key="ui_theme_pref" />
</PreferenceScreen>