Ok it is probably a h264 stream using a javascript player embedded in that webpage. It may even need a browser addon that you need to install before that page will show the video. Not having any Nest cameras I am only guessing and to confirm you would need to save the html file and look at the source, or right hand click and select ‘view source’ in some browsers will show you.
As for how to display it, probably the easiest way would be to display the html page using this technique..
Display the whole webpage and then use CSS to hide the areas of the page you don’t want after you have it working.