chromium/chrome/android/java/res/layout/custom_tabs_minimize_button.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
Copyright 2023 The Chromium Authors
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.
-->

<ImageButton
    xmlns:android="http://schemas.android.com/apk/res/android"
    style="@style/ToolbarButton"
    android:contentDescription="@string/custom_tab_minimize"/>