chromium/chrome/browser/autofill/android/java/res/drawable/store_locally_tooltip_background.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.
-->

<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <solid android:color="@color/baseline_neutral_0" />
    <corners android:radius="2dp" />
</shape>