chromium/android_webview/nonembedded/java/res_devui/values-night/styles.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
  Copyright 2019 The Chromium Authors
  Use of this source code is governed by a BSD-style license that can be
  found in the LICENSE file.
-->

<resources>
    <style name="Theme.DevUi.DayNight" parent="@android:style/Theme.Material" />
</resources>