Wrong scale factor for child windows

screenScale in PresentableState is always 0 for child windows (See RT-32888).

Because of it es2 pipeline doesn't work in applets:

java.lang.RuntimeException: Requested texture dimensions (0x0) require dimensions (0x0) that exceed maximum texture size (8192)
at com.sun.prism.es2.ES2RTTexture.create(ES2RTTexture.java:216)
at com.sun.prism.es2.ES2ResourceFactory.createRTTexture(ES2ResourceFactory.java:101)
at com.sun.prism.es2.ES2SwapChain.createGraphics(ES2SwapChain.java:211)
at com.sun.prism.es2.ES2SwapChain.createGraphics(ES2SwapChain.java:40)
at com.sun.javafx.tk.quantum.PresentingPainter.run(PresentingPainter.java:84)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
at com.sun.javafx.tk.RenderJob.run(RenderJob.java:58)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:129)
at java.lang.Thread.run(Thread.java:724)