Gnome Web, Midori, Falkon and Konqueror are browsers that only run on the "free" desktop, and don't support VAAPI/VDPAU either. Google built an entire OS based on Gentoo, and the desktop Linux build of Chrome doesn't support video acceleration either.

I think you should reconsider how easy it is to smoothly get an accelerated video buffer from a specific GPU component into an already heavily GPU optimized and dynamic web page. Web browsers have a lot more complicated graphics rendering problems to solve than VLC does.