Speaking for Chrome's implementation, efficiently rendering video on macOS does require CALayer compositing, but it's not sufficient.
Only certain types of decoded frames can be efficiently scanned out (different from the types that can be used efficiently in OpenGL compositing). Actually entering the most efficient fullscreen video mode requires some magic. Matching macOS behavior exactly when a fallback to OpenGL compositing is required can be difficult (eg. colorspace bugs can result in flickering).
I have not looked at the new code in Firefox, but I would expect that not all of the benefit would be realized in a first release. In any case it's a huge undertaking to support a single platform; congrats to the team for making it happen!
Speaking for Chrome's implementation, efficiently rendering video on macOS does require CALayer compositing, but it's not sufficient.
Only certain types of decoded frames can be efficiently scanned out (different from the types that can be used efficiently in OpenGL compositing). Actually entering the most efficient fullscreen video mode requires some magic. Matching macOS behavior exactly when a fallback to OpenGL compositing is required can be difficult (eg. colorspace bugs can result in flickering).
I have not looked at the new code in Firefox, but I would expect that not all of the benefit would be realized in a first release. In any case it's a huge undertaking to support a single platform; congrats to the team for making it happen!