Mainline Firefox still tears horribly on every platform where the WM doesn't transparently handle the draws. Will this be included for the entirety of the browser, or just B2G?
Syncing the compositor's page flips to vsync is already possible if you have hw layers on. Check about:support for GPU Accelerated Windows. It should also work in software if your display protocol supports explicit buffer flips - for example, the GTK3 version of Firefox.
edit: Firefox doesn't tear for me with GTK2 either, but I'm actually not sure why that is. Full screen videos tear with GTK2.
edit: Firefox doesn't tear for me with GTK2 either, but I'm actually not sure why that is. Full screen videos tear with GTK2.