All browsers have had GPU-accelerated rendering in some form for years now. Mobile Safari has had a GPU-accelerated compositor since 2007.
The primary difference between Chrome and Firefox Quantum Render (WebRender) is that Chrome maintains a distinction between painting and compositing, while WebRender mostly collapses the phases into a unified rendering step (and Pathfinder even more so). Everything in Chrome other than media and WebGL goes through a vector graphics API (Skia) before being handed to a compositor that draws tiles on screen. But WebRender renders CSS content directly to the screen, like a game would.
The primary difference between Chrome and Firefox Quantum Render (WebRender) is that Chrome maintains a distinction between painting and compositing, while WebRender mostly collapses the phases into a unified rendering step (and Pathfinder even more so). Everything in Chrome other than media and WebGL goes through a vector graphics API (Skia) before being handed to a compositor that draws tiles on screen. But WebRender renders CSS content directly to the screen, like a game would.