KR slows down twice:
1st time he lets Barrichelo through. That is into corner 1.
2nd time he lifts for corner 2, as does Barrichelo infront of him because they are both on the curb and for both the corner is tighter to take as they are on the inside.
If you compare the speed of Barri and KR and their respective distance it is always about the same (you can see it also in KR`s onboard).
BUT there is no sudden braking or whatever from KR side. Compare all the camera`s available. He lets Barri through and follows him through corner 2.
You seem to get the impression of KR dramatically slowing down because the other cars are not slowing down when approaching turn 2, because they are busy with themselves.