Winform unload

[madaster97]

In the WinForms minimal example, I noticed an issue where the "onunload" event doesn't seem to be firing if you click File > Exit. I think this is related to CefSharp issue #1574, where there's a bit of a race condition when you call browser.Dispose() before removing the browser from the holding control.

In my case, the website I'm trying to embed relies on the onunload event to fire an Ajax/fetch request that logs the user out. With the current example setup, the event is firing but (almost) every time the browser is torn down before the Ajax can send. I can even see the TCP/TLS connection for my Ajax call start (in Fiddler) but then don't see the request body sent out.

If I update the example to remove the browser from the control before Disposing the browser, I consistently see my calls complete!

toolStripContainer.ContentPanel.Controls.Remove(browser);

I think it would make sense to add this to the minimal example to show others a simple way to handle this, with a comment referencing the issue above. There are more complicated ways to handle this like implementing ILifespanHandler.DoClose. That and more already seems to be covered in the larger WinForms example.