Currently we don't have a way to pass the depthBuffer flag from Window to support renderToImage.

QuantumToolkit.java:
1213 void draw(com.sun.prism.Graphics g, int w, int h) {
1214 // TODO: get this from the ImageRenderingContext
1215 // (this will be a problem since we don't necessasrily have a Window)
1216 g.setDepthBuffer(PrismSettings.forceDepthBuffer);

We will need some sort of additional interface.