FULL PRODUCT VERSION :
java version "1.8.0_60"
Java(TM) SE Runtime Environment (build 1.8.0_60-b27)
Java HotSpot(TM) 64-Bit Server VM (build 25.60-b23, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.3.9600]

A DESCRIPTION OF THE PROBLEM :
If I embed Swing into JavaFX which is embedded into Swing, and I set focus with the mouse, I do have issues with the CPU usage.

this bug is related to bug JDK-8088540.

Lets start with this example:

public class EmbeddedTestWithFX extends JFrame {

    public EmbeddedTestWithFX() {
        setSize(new Dimension(300, 300));

        JTextArea textArea = new JTextArea();
        textArea.setSize(new Dimension(150, 150));

        JPanel container = new JPanel();
        container.setLayout(null);
        container.add(textArea);

        JFXPanel jfxPanel = new JFXPanel();

        Platform.runLater(() -> {
            SwingNode swing = new SwingNode();
            StackPane stack = new StackPane(swing);
            Scene scene = new Scene(stack);
            swing.setContent(container);
            SwingUtilities.invokeLater(() -> jfxPanel.setScene(scene));
        });

        setContentPane(jfxPanel);
    }

    public static void main(String[] args) {
        new EmbeddedTestWithFX().setVisible(true);
    }
}

If I then try to click on the JTextArea, I can see in the taskmanager, that it uses alot of CPU, around 25 procent of my CPU (Core I7-4810MQ 2.8GHz)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Click on the textarea, and the problem should be obvious

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Expecting that the CPU usage doesn't go up
ACTUAL -
It uses alot of CPU, around 25 procent of my CPU (Core I7-4810MQ 2.8GHz)

REPRODUCIBILITY :
This bug can be reproduced always.