chrome/android/java/res/layout/bottom_toolbar.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2018 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. -->

<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

  <include layout="@layout/bottom_toolbar_browsing" />

  <ViewStub
      android:id="@+id/bottom_toolbar_tab_switcher_mode_stub"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:inflatedId="@+id/bottom_toolbar_tab_switcher_mode"
      android:layout="@layout/bottom_toolbar_tab_switcher" />

</FrameLayout>