PaintCollector.done(RenderJob) contains the following code:

            // The embedded platform needs some indication when rendering
            // is finished so they can paint the stacking order and cursor
            // on machines that might not have a window manager.
            View.notifyRenderingEnd();

This code is dead, it's no-op in Glass. It was required a while ago, but is no longer needed as we are composing windows onto the cram buffer inside Prism.