Like many games before it, Relic Entertainments Warhammer 40,000: Dawn of War 2 - Chaos Rising has ditched the much-loathed Games for Windows Live integration.
Presumably, GFWL has been replaced with Steamworks, but the post announcing the change doesn't actually specify that.
It does have a few other significant changes though, including the removal of pausing in multiplayer games, referee mode, and LAN play. Ouch.