This is a regression caused by the recent work on proportional gradients in SoMa. The attached testcase throws the following exception:

Exception in thread "AWT-EventQueue-0" java.lang.UnsupportedOperationException:
ProportionalPaint is not designed to be used directly by rendering operations
        at com.sun.javafx.tk.swing.Gradients$ProportionalGradientDelegate.createContext(Gradients.java:118)
        at sun.java2d.pipe.AlphaPaintPipe.startSequence(AlphaPaintPipe.java:65)
        at sun.java2d.pipe.SpanShapeRenderer$Composite.startSequence(SpanShapeRenderer.java:38)
        at sun.java2d.pipe.SpanShapeRenderer.renderRect(SpanShapeRenderer.java:143)
        at sun.java2d.pipe.SpanShapeRenderer.fill(SpanShapeRenderer.java:87)
        at sun.java2d.pipe.PixelToShapeConverter.fillRect(PixelToShapeConverter.java:44)
        at sun.java2d.pipe.ValidatePipe.fillRect(ValidatePipe.java:58)
        at sun.java2d.SunGraphics2D.fillRect(SunGraphics2D.java:2265)
        at com.sun.scenario.effect.impl.j2d.J2DFloodPeer.filter(J2DFloodPeer.java:77)

Looks like we need to update J2DFloodPeer to deal with the new factory approach in ProportionalPaint. (The Prism stack is not affected by this issue because it does not rely on the ProportionalPaint class.)