Alt menus (mnemonics) do not work properly

We are facing an issue in our application where our menu bar and items are not properly reachable when using alt + mnemonics from inside the webview.

Reproducible code is below:

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;

using Microsoft.Web.WebView2.WinForms;

namespace WebView2BugMnemonics
{
    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(CreateTestForm());
        }

        public static Form CreateTestForm()
        {
            var form = new Form
            {
                Size = new Size(1280, 1024)
            };

            var menuStrip = new MenuStrip
            {
                Dock = DockStyle.Top
            };
            var soundMenuItem = new ToolStripMenuItem("Sound", null, new ToolStripMenuItem("Switch on"));
            var settingsMenuItem = new ToolStripMenuItem("Settings", null, soundMenuItem);
            menuStrip.Items.Add(settingsMenuItem);


            var webView2 = new WebView2
            {
                Dock = DockStyle.Fill,
                Source = new Uri(@"about:blank")
            };
            webView2.CoreWebView2Ready += (sender, e) =>
            {
                webView2.CoreWebView2.Navigate("https://www.google.com");
            };


            var textBox = new TextBox
            {
                Dock = DockStyle.Bottom
            };

            form.Controls.Add(menuStrip);
            form.Controls.Add(webView2);
            form.Controls.Add(textBox);

            return form;
        }
    }
}

When you put the focus in the textbox and press Alt + S + S + S/Enter the 'Switch on' menu item will get executed, however when you perform exactly the same actions in the search bar on Google within the webview it does not work as expected. We expect it to work the same as compared to when executing it in the textbox.

AB#27801085

Start at CreateTestForm and the WebView2 CoreWebView2Ready handler in the provided reproduction. Compare Alt+mnemonic handling in the TextBox with the Google search bar inside WebView2. Done means the same Alt+S+S+S/Enter sequence reaches and executes the Switch on menu item from both controls.