Google hangouts in Chrome uses Native Client. Which no other browser vendor has any interest in supporting. Webassembly is the path forward for such code as it is supported/planned support in Firefox, Edge, Chrome and Safari. They have had 18 months of notice that the end of plugins was coming.

I think a large part of the problem is how many diverse applications are now being served through the browser. Interop always had problems and this is just the natural evolution of old issues like bad CSS rendering.