with the following test code and usage like average browser. The memory consumption went up to 800m+ in task manager (increased rapidly if constantly re-sizing the frame).

import javax.swing.JFrame;

import javafx.application.Platform;
import javafx.beans.value.InvalidationListener;
import javafx.beans.value.ObservableValue;
import javafx.embed.swing.JFXPanel;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.web.WebEngine;
import javafx.scene.web.WebView;

/**
 * @author rdong
 */
public class BrowserPanel
    extends JFXPanel
{

    private WebView browser;

    private WebEngine webEngine;

    private Scene scene;

    public BrowserPanel(final String url)
    {
        Platform.runLater(new Runnable()
        {
            public void run()
            {
                createBrowserScene(url);
            }
        });
    }

    /**
     * @param url
     *
     */
    protected void createBrowserScene(String url)
    {
        Group root = new Group();
        setScene(scene = new Scene(root));
        root.getChildren().add(browser = new WebView());
        webEngine = new WebEngine(url);
        browser.setEngine(webEngine);
        scene.widthProperty().addListener(new InvalidationListener()
        {
            @Override
            public void invalidated(ObservableValue ov)
            {
                browser.resize(scene.getWidth(), scene.getHeight());
            }
        });
        scene.heightProperty().addListener(new InvalidationListener()
        {
            @Override
            public void invalidated(ObservableValue ov)
            {
                browser.resize(scene.getWidth(), scene.getHeight());
            }
        });
        browser.widthProperty().addListener(new InvalidationListener()
        {
            @Override
            public void invalidated(ObservableValue ov)
            {
                browser.resize(scene.getWidth(), scene.getHeight());
            }
        });
        browser.heightProperty().addListener(new InvalidationListener()
        {
            @Override
            public void invalidated(ObservableValue ov)
            {
                browser.resize(scene.getWidth(), scene.getHeight());
            }
        });
    }
    
    public static void main(String[] args)
    {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setSize(500, 400);
        f.getContentPane().add(new BrowserPanel("http://yahoo.com"));
        f.setVisible(true);
    }
}