chrome/android/java/res/drawable-sw600dp/window_background.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2015 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. -->

<layer-list
    xmlns:android="http://schemas.android.com/apk/res/android" >
    <item>
        <shape android:shape="rectangle">
            <solid android:color="@android:color/black" />
        </shape>
    </item>
    <item
        android:top="25dp"
        android:bottom="0px">
      <nine-patch android:src="@drawable/toolbar_background" />
  </item>
</layer-list>