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

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

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/browser_toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:elevation="4dp" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:orientation="horizontal"
        tools:ignore="NestedWeights">

        <androidx.fragment.app.FragmentContainerView
            android:id="@+id/profile_one_browser_container"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1" />

        <View
            android:layout_width="4dp"
            android:layout_height="match_parent"
            android:background="#ABABAB" />

        <androidx.fragment.app.FragmentContainerView
            android:id="@+id/profile_two_browser_container"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1" />
    </LinearLayout>
</LinearLayout>