Right now we do not take into account the fill-rule for polygon interpolation, however http://dev.w3.org/csswg/css-shapes/#basic-shape-interpolation says we should: If both shapes are of type polygon(), both polygons have the same number of vertices, and use the same <fill-rule>, interpolate between each value in the shape functions.
Created attachment 218870 [details] Patch
Landed in r160429.