I suspect you will need to speak to Microsoft, Google and Firefox for starters.
With webhelp it is possible to call the help in what was referred to as a chromeless window. That is nothing to do with the Chrome browser but about the fact that the window did not have any trim (as in chrome on a car). That was something that had to be done by the developers.
I don't know if that is also possible with responsive help but it is something your developers would have to look into, unless someone here has done it. I have not seen any reports of others wanting to or having done that.