"rapid advances in Chrome's 2D graphics performance"

I'd assume it's the 2D graphics performance.

And this is just one part of page rendering. This part may already be neglectable, representing fractions of a second, drowning in the parsing and structuring of the output done prior to actually rendering it.

To me, all of this is just windbagging and vacuous marketing - just like the (almost entirely) pointless Javascript boasting.