She's known for being able to break the fourth wall (unlike the other ponies in FiM) and doing other "impossible" things, which I'm figuring the hacker may have connected to breaking out of a sandbox.
You may also want to see: https://secure.wikimedia.org/wikipedia/en/wiki/My_Little_Pon...
He guessed "some predictable addresses allocated by Windows" though. Not detracting from the achievement, but this could arguably be stashed in the non-Chrome side of things.
I ask, as wish to know at a high level what tools and code they are using to find and exploit Chrome.