Large filled circles fill the opposite side.

Code example:

``` javascript
var circle = new Cesium.Polygon();
circle.setPositions(
Cesium.Shapes.computeCircleBoundary(
ellipsoid,
ellipsoid.cartographicToCartesian(Cesium.Cartographic.fromDegrees(0, 90.0)), 12500000.0));
primitives.add(circle);
```

Reproduce the issue using the JavaScript example, then trace Cesium.Polygon and Cesium.Shapes.computeCircleBoundary to determine why a circle centered at 90 degrees fills the opposite side. Done means the large filled circle renders only on its intended side; no source files or tests are named in the issue.

Written by the indexing model from the issue text.