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

<?xml version="1.0" encoding="utf-8"?>
<!--
Copyright 2015 The Chromium Authors
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.
-->
<org.chromium.chrome.browser.customtabs.CustomTabBottomBarView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    app:maxHeight="@dimen/custom_tabs_bottom_bar_max_height" >

    <View
        android:id="@+id/bottombar_shadow"
        android:layout_width="match_parent"
        android:layout_height="4dp"
        android:background="@drawable/infobar_shadow_top" />

</org.chromium.chrome.browser.customtabs.CustomTabBottomBarView>