I googled it, and --dump-dom simply dumps the output of document.body.innerHTML. I have not used headless chrome at all, but I imagine it would not be that hard

I googled it, and --dump-dom simply dumps the output of document.body.innerHTML. I have not used headless chrome at all, but I imagine it would not be that hard to get it to dump document.documentElement.outerHTML instead. (execute JavaScript on the page is most likely possible?)