One of Chrome's most iconic features (get it?) is getting the boot. The wrench icon, that's been around from the get go and served as the way to access any sort of settings or advanced features, is getting replaced by a new "hotdog" icon. That's the official name anyway, but it's probably not the one that's going to get pushed to the public.
It may look like a minor change and it is, just replace the graphics and you're done. But, for one, you have to do it for all Chrome versions across all platforms. The big problem though is that the change affects a lot more things than Chrome.
For one, a lot of documentation is going to have to get updated and references to the "wrench menu" replaced with ones to the "hotdog menu" or whatever Google ends up calling it. If anything, it looks more like a hamburger. The feature is slated to land in Chrome 22, if the team can manage it.