javax.swing.JDesktopPane/getAllFrames() returns invalid value in GTK+ LAF

FULL PRODUCT VERSION :
Java(TM) SE Runtime Environment (build 1.6.0-b105)
Java HotSpot(TM) Client VM (build 1.6.0-b105, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
libgtk 2.10.6, KDE: 3.5.5

A DESCRIPTION OF THE PROBLEM :
Documentation [1] for JDesktopPane states that getAllFrames "Returns iconified frames as well as expanded frames.". However, in GTK+ look and feel it returns only expanded frames.

[1] http://java.sun.com/javase/6/docs/api/javax/swing/JDesktopPane.html#getAllFrames()

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the attached test case. It should throw assertion error.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
getAllFrames should always return all iconified and all expanded frames.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import javax.swing.*;
public class Test extends JFrame {
JDesktopPane desktop;

Test() {
super("Test JDesktop");
setDefaultCloseOperation(EXIT_ON_CLOSE);
setSize(800, 600);

// create desktop and frames
desktop = new JDesktopPane();
add(desktop);
JInternalFrame frame1 = createFrame("1");
desktop.add(frame1);
JInternalFrame frame2 = createFrame("2");
desktop.add(frame2);

// minimize frames
makeIcon(frame1);
//makeIcon(frame2);

// test Metal
testLAF("javax.swing.plaf.metal.MetalLookAndFeel");
// test GTK+
testLAF("com.sun.java.swing.plaf.gtk.GTKLookAndFeel");

setVisible(true);
}

void testLAF(String clazz) {
System.err.println(clazz);
try {
UIManager.setLookAndFeel(clazz);
SwingUtilities.updateComponentTreeUI(this);
int numFrames = desktop.getAllFrames().length;
if (numFrames != 2)
throw new AssertionError("desktop.getAllFrames().length != 2 (" + numFrames + ") in " + clazz);
}
catch (Exception e) {
e.printStackTrace();
}
}

JInternalFrame createFrame(String title) {
JInternalFrame f = new JInternalFrame(title);
f.setSize(100, 100);
f.setVisible(true);

return f;
}

void makeIcon(JInternalFrame f) {
try {
f.setIcon(true);
}
catch (java.beans.PropertyVetoException e) {
e.printStackTrace();
}
}

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

}
---------- END SOURCE ----------