It's not gnome's own engine at all, it's the forked-a-long-time-ago from KDE's KHTML, adopted by Apple and significantly improved internally under the WebCore project/framework with changes shared from time to time with KDE devs before it was hard-forked as webkit and developed more in the open, then adopted by Chrome/Chromium (before Google hard-forked and renamed it to blink), with gnomifications for integrations and wrappers for the GTK userland.