mDegree should be how much to rotate by this frame. It should not grow with time. What rotate() is doing is increase the rotation speed.
EDIT: Wait... I think I see what the others are seeing now. Is it possible that mOrigins and mPoints are actually the same thing?
FURTHER EDIT: What does this line do?Point npoint = mPoints.get(i);
There are two lists of points inside the polygon class. The original points mOrigin and the current points mPoints. mPoints changes and mOrigin does not with the rotation.
That code takes the point i from mPoints and updates it.
The rotate method just applies the .5f to increase the degree... The speed never increases, its always .5f and mDegree is increased by that amount each update.