Google has come out with the 'baap' of Low level page rendering development tool, Speed Tracer. It will display all reflows, CSS calculations, etc. Find more about Speed Tracer

Chrome is great, blah blah.. But I don't see web developers will use Google Chrome while developing until they have some addons like Firefox sports. Some of the life savers required are

1. Live HTTP Headers
2. Firebug
3. Web Developer Toolbar