I've had the exact same thing happen before!!! It was a f*cking chrome extension!!!
They update automatically and can become malware without you being able to do anything about it!!!
I thought lastpass was changing the addresses on me, and I tried turning it off, and turning off autofill and everything.
Nothing worked, and then I found that it was a bitcoin price notification extension (i found out by searching for the address it was sent to, and found others posting about similar problems) I checked yours, google didn't say anything, though it could be a new virus.
I asked a google developer about how this could happen, he said: "Just turn off autoupdate" -- that is not possible from what I see, and he couldn't figure it out either.
be super careful with Chrome Extensions
I can digup more info on this if you need it. Good luck! I hope it wasn't this, and BTer can somehow give you back your BTC