I mean, Linux doesn't have a common native notification center. You have to install libnotify and have a notification server to use it. Granted, most distros will do it for you, but it's not really the same as OSX/Windows.
By the same token it doesn't even have a window system, I don't think it is a good argument.
Chrome/chromium should simply depend on libnotify, just like it depends on gtk2.