chrome/android/java/res/drawable/snackbar_background_tablet.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. -->

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

    <solid android:color="@color/snackbar_background_color" />

    <corners
        android:topLeftRadius="2dip"
        android:topRightRadius="2dip"/>

</shape>