chrome/android/java/res/drawable/tab_indicator.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. -->
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:left="@dimen/tab_indicator_padding"
        android:right="@dimen/tab_indicator_padding" >
        <shape android:shape="rectangle" >
            <corners
                android:topRightRadius="@dimen/tab_indicator_radius"
                android:topLeftRadius="@dimen/tab_indicator_radius" />
        </shape>
    </item>
</layer-list>