AMD just so happen to have a semi custom chip business and arm server cpu ready to roll out in 2014. My money is this is amd behind this. It's freaking brilliant, instead of going toe to toe with Intel you offer a service Intel customers need at a fraction of the cost. Sure you wont be making 2-3k per server chip but you hurt the comptetition while bringing in revenue that previously wasnt there
AMD embedded business isn't about making bleeding edge custom designs to customers, but slighting modifying AMD standard IP and adding the customer's IP to a given design. This is not what Google wants, if the rumor is correct they would be aiming for a proprietary design, a custom design, not semi custom.
And unless Google workloads were to run on the specific IP blocks only, Google would get the same AMD Piledriver/Kabini dogs of today, but with some fancy custom blocks that would not be able to save the day.
I'm kinda skeptical about Google pursuing that route. They would have to bear the brunt of the entire validation of the chip for servers, an expense that would be waaaay higher than, let's say, console chips and they would have to spend a lot of money in updating the chip otherwise they would be left behind in the industry. I doubt any amount of custom IP would be able to improve performance enough to justify the costs.
A custom architecture is even worse. IBM Power is being licensed because its market is shrinking and Itanium is dying. Google would not be dumb enough to go down on that hole too.