They have a mac team that have been working on chrome for a long time. Maybe they are very small compared to the windows team, and that's the only reason why it's taking so long to have an OSX version, but from the blog post it seems to me that they are having problems with the shared code.
Maybe I'm reading a different blog post, but the one I saw says things like this:
Over the last couple of months, the group working on Mac Chrome (myself included) has shifted gears from layout tests and WebKit compatibility to getting the application user interface up and limping.
To me, this says that their first priorities were to establish a regression testing framework to make sure that they didn't deliver something that rendered badly. Good choice, in my opinion. Maybe you were refering to this, though:
Last week, while I was in Cali, the entire team made a tremendous amount of progress getting the cross-platform model and controller classes scaffolded, topped off with a Cocoa UI...
...but this does not say to me that they are having problems with cross-platform code. Rather, this says to me that they are just now in the process of creating it...as in: prior to their efforts, it did not exist.