chromium/android_webview/tools/system_webview_shell/apk/res/layout/activity_webview_browser.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.
-->

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:gravity="center">

  <androidx.appcompat.widget.Toolbar
      android:id="@+id/browser_toolbar"
      android:layout_width="match_parent"
      android:layout_height="?attr/actionBarSize"
      android:elevation="4dp" />
  <androidx.fragment.app.FragmentContainerView
      android:id="@+id/container"
      android:layout_width="match_parent"
      android:name="org.chromium.webview_shell.WebViewBrowserFragment"
      android:layout_height="0dp"
      android:layout_weight="1" />

</LinearLayout>