Winforms Control Invalidate OnResize

Addresses an issue when hosting the WinForms control in a simple panel that upon resize it's contents aren't redrawn.

Updates the example to include an easy to validate representation.
So with https://github.com/amaitland/CefSharp/commit/0856afaabe89c0a715c2ca3c980d6346d2593a3d this isn't needed anymore?