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

<?xml version="1.0" encoding="UTF-8"?>
<!--
Copyright 2024 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">
     <solid android:color="@color/incognito_tab_bg_color"/>
     <corners android:radius="@dimen/modern_toolbar_background_corner_radius" />
</shape>