Make sure the theta is correctly represented and incoming polygon is CW for shadow.

Now the theta = 0 should be on +x axis.
And cos(theta) should correctly represent x value.
Without this fix, the poly theta (from atan2) can be wrongly rotated 90 degrees.

Also, make sure the incoming polygon is CW for the shadow system.
This fix visual artifacts in recent regression for spot shadows.

bug:13553955

Change-Id: I9bbf54db094e7f133326da4dae4610962da849c1