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

<?xml version="1.0" encoding="utf-8"?>
<!--
Copyright 2021 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"
    android:shape="rectangle">
    <corners
        android:radius="1dp"
        android:topLeftRadius="@dimen/custom_tabs_default_corner_radius"
        android:topRightRadius="@dimen/custom_tabs_default_corner_radius"
        android:bottomLeftRadius="0dp"
        android:bottomRightRadius="0dp" />
    <solid
        android:color="@macro/default_bg_color" />
</shape>