chrome/android/java/res/drawable/modern_toolbar_background_white.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2018 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. -->

<shape
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >
    <solid android:color="@android:color/white" />
    <size
        android:width="@dimen/modern_toolbar_background_size"
        android:height="@dimen/modern_toolbar_background_size" />
    <corners android:radius="@dimen/modern_toolbar_background_corner_radius" />
</shape>