JIT makes Nitro faster, and Nitro makes Mobile Safari faster. The technical details aren't too important here - John Gruber has a good explanation here, if you want it - but the effects are. Mobile Safari, the default browser in iOS, uses a Javascript engine called Nitro, which in turn uses a technology called 'just-in-time' compilation, or JIT, to execute scripts more quickly. And barring some kind of special exemption, it's virtually guaranteed the Chrome for iOS will have to use the same slower browser engine that Facebook has been suffering with.
So why the sudden change of course? Because in-app browsers are required to suck in iOS. Until now, Facebook's app has been based on web tech - it's a browser and a mobile site inside of a blue-colored wrapper, basically. Facebook revealed yesterday that it is finally making a real, fully native iOS app.
