I saw this model has 512Mb of VRAm and we know that in some case Chrome & Hangout take a lot of resource so I was just speculating, if you have the same behavior without any other program the problem come from something else..
Well, mine DOES have 1GiB of VRAM as this version of the MacBook Pro does not ship with less. Once I get my PC running again I'll test on another set of Hardware.