Kristian and I were discussing supporting polygons with holes in the Shapefile to CZML converter. Our plan is to form a single polygon from the two boundaries by inserting a line segment between two mutually visible vertices. See Section 4 in Eberly’s paper -
http://www.geometrictools.com/Documentation/TriangulationByEarClipping.pdf. This will relieve work from the client and works with our ear clipping algorithm. Longer term, we can imagine even moving ear clipping to the server when/if CZML support basic meshes like indexed triangle lists (that is not a feature request).
Although the mutually visible vertices code will initially reside in the Shapefile converter, I see this going into a library of its own with other server-side geometric computations as needed.