How to add fullscreen support to a GeckoFx browser?

I'm building a web browser in a C# .NET Windows Form Application and wanted to add support for fullscreen usage (mainly on HTML5 videos).

So that when users press the fullscreen button on a video like a youtube video, the video would take up the full screen.

The browser uses a GeckoFx control to view the interweb. How would I go about doing this?

#c-sharp