chromium/chrome/android/webapk/shell_apk/res/values/default_enabled_activity.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
Copyright 2020 The Chromium Authors
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.
-->

<resources xmlns:android="http://schemas.android.com/apk/res/android">
    <bool name="opaque_main_activity_enabled_default">false</bool>
    <bool name="transparent_main_activity_enabled_default">true</bool>
</resources>