use `win.` in `.viewport`

[emirotin]

We had an issue on some 3rd party site due to self being globally rewritten by other script While that's obviously not Bonzo's fail it's quite possible to accure due to non-experienced programmers copying self = this pattern and forgetting var.

I think the change is also healthy due to making the code more consistent — that was actually the only place referencing to self.

[rvagg]

I'm cool with this, @ded?

[ded]

hmm... wonder why this isn't merging..

[ded]

merged