ADDITIONAL SYSTEM INFORMATION :
Windows desktop itself has some customizations. My desktop is customized to 'classic' (to reduce the noise of the newer versions).
Windows 10, with all the current updates, 1903
Java 8 211
Thinkpad x250 (i7)

A DESCRIPTION OF THE PROBLEM :
I previously filed a bug (JDK-8225502) which was closed as being not reproducible. Unfortunately, I have two laptops both of which (out of 7) have the problem and it is fully reproducible.

It is possible that this is happening in 'touch-screen' computers only. Both machines are touch-screen.

Below is the thread-dump (control-break), I hope this will help understand where it is hanging.
--------------------------------------------------------------------------------------------------------------------------
C:\Users\Alamgir Farouk\Desktop>java -jar test.jar
2019-06-11 20:32:10
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.211-b12 mixed mode):

"JavaFX-Launcher" #15 prio=5 os_prio=0 tid=0x00000000199f6800 nid=0xc58 waiting on condition [0x000000001f0de000]
   java.lang.Thread.State: WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for <0x00000000d69e6940> (a java.util.concurrent.CountDownLatch$Sync)
        at java.util.concurrent.locks.LockSupport.park(Unknown Source)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(Unknown Source)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(Unknown Source)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(Unknown Source)
        at java.util.concurrent.CountDownLatch.await(Unknown Source)
        at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:873)
        at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$159(LauncherImpl.java:182)
        at com.sun.javafx.application.LauncherImpl$$Lambda$51/1789447862.run(Unknown Source)
        at java.lang.Thread.run(Unknown Source)

"Thread-2" #14 daemon prio=5 os_prio=0 tid=0x0000000019a28800 nid=0x1664 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"JavaFX Application Thread" #13 prio=5 os_prio=0 tid=0x0000000019951000 nid=0x2d0c runnable [0x000000001a60e000]
   java.lang.Thread.State: RUNNABLE
        at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
        at com.sun.glass.ui.win.WinApplication.lambda$null$152(WinApplication.java:177)
        at com.sun.glass.ui.win.WinApplication$$Lambda$37/1642360923.run(Unknown Source)
        at java.lang.Thread.run(Unknown Source)

"Thread-1" #12 daemon prio=5 os_prio=0 tid=0x000000001994d000 nid=0x1e48 waiting on condition [0x000000001a50e000]
   java.lang.Thread.State: WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for <0x00000000d6527810> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
        at java.util.concurrent.locks.LockSupport.park(Unknown Source)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(Unknown Source)
        at java.util.concurrent.LinkedBlockingDeque.takeFirst(Unknown Source)
        at com.sun.glass.ui.InvokeLaterDispatcher.run(InvokeLaterDispatcher.java:108)

"QuantumRenderer-0" #10 daemon prio=5 os_prio=0 tid=0x00000000195d2800 nid=0x8f8 waiting on condition [0x000000001a23e000]
   java.lang.Thread.State: WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for <0x00000000d63ec490> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
        at java.util.concurrent.locks.LockSupport.park(Unknown Source)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(Unknown Source)
        at java.util.concurrent.LinkedBlockingQueue.take(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor.getTask(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:125)
        at java.lang.Thread.run(Unknown Source)

"Service Thread" #9 daemon prio=9 os_prio=0 tid=0x0000000019239800 nid=0x2e58 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C1 CompilerThread2" #8 daemon prio=9 os_prio=2 tid=0x00000000178cb000 nid=0x3664 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread1" #7 daemon prio=9 os_prio=2 tid=0x00000000178c4800 nid=0x1f88 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread0" #6 daemon prio=9 os_prio=2 tid=0x00000000178bb800 nid=0x2184 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x00000000178c6800 nid=0x247c runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x00000000178c5800 nid=0xe74 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Finalizer" #3 daemon prio=8 os_prio=1 tid=0x00000000178aa800 nid=0x1cc4 in Object.wait() [0x0000000018c0f000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x00000000d5f88ed0> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(Unknown Source)
        - locked <0x00000000d5f88ed0> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(Unknown Source)
        at java.lang.ref.Finalizer$FinalizerThread.run(Unknown Source)

"Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x0000000017889000 nid=0x1884 in Object.wait() [0x0000000018b0f000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x00000000d5f86bf8> (a java.lang.ref.Reference$Lock)
        at java.lang.Object.wait(Unknown Source)
        at java.lang.ref.Reference.tryHandlePending(Unknown Source)
        - locked <0x00000000d5f86bf8> (a java.lang.ref.Reference$Lock)
        at java.lang.ref.Reference$ReferenceHandler.run(Unknown Source)

"main" #1 prio=5 os_prio=0 tid=0x0000000002ca1000 nid=0x78 waiting on condition [0x0000000002bed000]
   java.lang.Thread.State: WAITING (parking)
        at sun.misc.Unsafe.park(Native Method)
        - parking to wait for <0x00000000d6955498> (a java.util.concurrent.CountDownLatch$Sync)
        at java.util.concurrent.locks.LockSupport.park(Unknown Source)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(Unknown Source)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(Unknown Source)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(Unknown Source)
        at java.util.concurrent.CountDownLatch.await(Unknown Source)
        at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:200)
        at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:143)
        at javafx.application.Application.launch(Application.java:252)
        at com.alam33.Win10_1903Test.main(Win10_1903Test.java:36)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
        at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at sun.launcher.LauncherHelper$FXHelper.main(Unknown Source)

"VM Thread" os_prio=2 tid=0x0000000017887800 nid=0x19ac runnable

"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x0000000002cb7000 nid=0x3080 runnable

"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x0000000002cb9000 nid=0x2d1c runnable

"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x0000000002cba800 nid=0x1f38 runnable

"GC task thread#3 (ParallelGC)" os_prio=0 tid=0x0000000002cbd000 nid=0x203c runnable

"VM Periodic Task Thread" os_prio=2 tid=0x000000001925b000 nid=0xa74 waiting on condition

JNI global references: 496

Heap
 PSYoungGen total 38400K, used 18638K [0x00000000d5f80000, 0x00000000d8a00000, 0x0000000100000000)
  eden space 33280K, 56% used [0x00000000d5f80000,0x00000000d71b3830,0x00000000d8000000)
  from space 5120K, 0% used [0x00000000d8500000,0x00000000d8500000,0x00000000d8a00000)
  to space 5120K, 0% used [0x00000000d8000000,0x00000000d8000000,0x00000000d8500000)
 ParOldGen total 87552K, used 0K [0x0000000081e00000, 0x0000000087380000, 0x00000000d5f80000)
  object space 87552K, 0% used [0x0000000081e00000,0x0000000081e00000,0x0000000087380000)
 Metaspace used 9803K, capacity 10208K, committed 10496K, reserved 1058816K
  class space used 1296K, capacity 1429K, committed 1536K, reserved 1048576K







STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Same as described in JDK-8225502


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Stage is shown
ACTUAL -
Stage not shown, but task manager shows small icon.
If the application is run via Eclipse, we may need to use TaskManager to kill java process

---------- BEGIN SOURCE ----------
package com.alam33;

import java.io.IOException;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
import javafx.stage.StageStyle;

public class Win10_1903Test extends Application {

public Win10_1903Test() {

}

@Override
public void start(Stage primaryStage) throws IOException {

VBox vbox = new VBox();
vbox.setPrefHeight(200);
vbox.setPrefWidth(300);
Scene scene = new Scene(vbox);
primaryStage.setTitle("Win10_1903Test");
primaryStage.setScene(scene);

/* THIS IS THE OFFENDING LINE */
primaryStage.initStyle(StageStyle.UNDECORATED);

primaryStage.show();

}

public static void main(String[] args) {

launch(args);
}

}

---------- END SOURCE ----------

FREQUENCY : always