chromium/chrome/android/java/res/drawable/distilled_page_prefs_button_bg.xml

<?xml version="1.0" encoding="utf-8"?>

<!--
Copyright 2014 The Chromium Authors
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.
-->

<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_checked="true">
        <shape android:shape="rectangle">
          <solid android:color="@color/distilled_page_prefs_selected"/>
          <corners android:radius="16dp"/>
        </shape>
    </item>
    <item
        android:drawable="@android:color/transparent"
        android:state_checked="false" />
</selector>