According to Anandtech it's a Samsung brand SSD.
The largest SSD maker in the world is Samsung. Samsung makes the drives offered by Apple in its entire MacBook/MacBook Pro lineup. Samsung makes the drives you get if you order a Lenovo X300. In fact, if you're buying any major OEM system with an SSD in it, Samsung makes that drive.
I spoke with a few of the guys at work that replace these and they told me that they don't really pay attention to the brands, It's OEM. But the ones that he could remember where Samsung and Seagate.
Now this doesn't speak to the brand that ships, but just what is replaced (if needed) when you bring it in for repair.