8248381: Create a daemon thread for MonocleTimer

Reviewed-by: kcr, jvos

Author: jgneff

modules/javafx.graphics/src/main/java/com/sun/glass/ui/monocle/MonocleTimer.java

@@ -34,6 +34,8 @@
  * Monocle implementation class for Timer.
  */
 final class MonocleTimer extends Timer {
+    private static final String THREAD_NAME = "Monocle Timer";
+
     private static ScheduledThreadPoolExecutor scheduler;
     private ScheduledFuture<?> task;
 
@@ -51,7 +53,11 @@ static int getMaxPeriod_impl() {
 
     @Override protected long _start(final Runnable runnable, int period) {
         if (scheduler == null) {
-            scheduler = new ScheduledThreadPoolExecutor(1);
+            scheduler = new ScheduledThreadPoolExecutor(1, target -> {
+                Thread thread = new Thread(target, THREAD_NAME);
+                thread.setDaemon(true);
+                return thread;
+            });
         }
 
         task = scheduler.scheduleAtFixedRate(runnable, 0, period, TimeUnit.MILLISECONDS);