Create a second layer. Copy and paste the frames from the first layer. Tint the begining and ending keyframes of the second layer a slightly different color. This will help to create the illusion of going around the corner.
Step4:
On layer 1 in the "Transform" panel select "skew" and enter 3.0 and -3.0. Do this for the first and last keyframes.
On layer 2 do the same except enter 3.0 and 3.0. This gives us our different angles for each side of the corner.