chromium/components/browser_ui/widget/android/java/res/drawable-v23/sheet_background.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
Copyright 2022 The Chromium Authors
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.
-->

<shape
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
  <solid android:color="@color/sheet_bg_color_baseline" />
</shape>