chrome/browser/touch_to_fill/android/internal/java/res/drawable/touch_to_fill_credential_background.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2019 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">

    <stroke android:width="1dp" android:color="@color/hairline_stroke_color"/>
    <corners android:radius="8dp"/>
</shape>