Besides battery life, Chrome on the Mac prevents sleep indefinitely sometimes. If you check with pmset -g assertions, you'll see Chrome saying "WebRTC has active PeerConnections".
No thanks Google, you shouldn't get to decide when my PC goes into sleep mode.
I really hope Safari is better than that...
Edit: just as i'm typing this, Chrome has:
pid 19325(Google Chrome): [0x001ccbbb00018b19] 01:55:40 NoIdleSleepAssertion named: "WebRTC has active PeerConnections"
2 hours for... what? I have no idea which page is guilty.