LifeSpanHandler.cs

using System;
using System.Windows.Forms;
using CefSharp;
using CefSharp.WinForms;

namespace WindowsFormsApp1
{
    public class LifeSpanHandler : ILifeSpanHandler
    {
        private Form1 _form;

        public LifeSpanHandler(Form1 form)
        {
            _form = form;
        }

        public bool DoClose(IWebBrowser browserControl, IBrowser browser)
        {
            if (browser.IsPopup)
            {
                // Get the browser handle
                var browserHandle = browser.GetHost().GetWindowHandle();

                // Get the host control
                var parent = Control.FromChildHandle(browserHandle);

                // Get the parent tab
                if (parent.Parent is TabPage tab)
                {
                    // Close the tab 
                    _form.CloseTab(tab);
                }
            }

            return true;
        }

        public void OnAfterCreated(IWebBrowser browserControl, IBrowser browser)
        {
            if (browser.IsPopup)
            {
                // Get the browser handle
                var browserHandle = browser.GetHost().GetWindowHandle();

                // Get the host control
                var parent = Control.FromChildHandle(browserHandle);

                // Get the parent tab
                if (parent.Parent is TabPage tab)
                {
                    // Set the browser
                    tab.Tag = browserControl;
                }
            }

        }

        public void OnBeforeClose(IWebBrowser browserControl, IBrowser browser)
        {
        }

        public bool OnBeforePopup(IWebBrowser browserControl, IBrowser browser, IFrame frame, string targetUrl, string targetFrameName, WindowOpenDisposition targetDisposition, bool userGesture, IPopupFeatures popupFeatures, IWindowInfo windowInfo, IBrowserSettings browserSettings, ref bool noJavascriptAccess, out IWebBrowser newBrowser)
        {
            newBrowser = null;

            (browserControl as ChromiumWebBrowser).Invoke(new Action(() =>
            {
                // Create a new browser tab
                var control = _form.AddNewPopup(targetUrl);

                var rect = control.ClientRectangle;

                // Set the new window as a child of the new browser tab
                windowInfo.SetAsChild(control.Handle, rect.Left, rect.Top, rect.Right, rect.Bottom);
            }));

            return false;
        }
    }
}