Parent.getStylesheets().add(xxx) will cause a memory leak

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main.css (bg.png size: 85.2K)
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#bg
{
    -fx-background-image : url('images/bg.png');
    -fx-background-size: stretch;
    -fx-background-position: left top;
    -fx-background-repeat: no-repeat;
}

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CssMemoryLeakTest.java
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public class CssMemoryLeakTest extends Application {

    private StackPane root;
    private Button btn;

    @Override
    public void start(Stage primaryStage) {
        btn = new Button();
        btn.setText("Say 'Memory Leak'");
        btn.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                VBox box = new VBox();
                box.getStylesheets().add(getClass().getResource("resource/main.css").toExternalForm());
                box.setId("bg");
                root.getChildren().setAll(box, btn);
            }
        });

        root = new StackPane();
        root.getChildren().add(btn);

        Scene scene = new Scene(root, 300, 250);

        primaryStage.setTitle("Hello World!");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}


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It just took 4MB at the begining，
after clicking the button 20 times, the memory increase to 200MB

But, applying the same css file to the Scene, that would not happen


BTW: It took me 2 days to locate this problem... orz