FULL PRODUCT VERSION :
Java 1.6.0_39 and also Java 1.7.0_13

ADDITIONAL OS VERSION INFORMATION :
Windows 8 6.2

A DESCRIPTION OF THE PROBLEM :
The JScrollPane shows scrollbars with unmotivated 3 black lines inside (dirty regions).

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
start the application and watch the scrollbar in the JDialog with a JTree inside. 3 black lines are shown across he scrollbar.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
no black lines across a scrollbar
ACTUAL -
3 black lines across a scrollbar

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package com.classwizard.cw;


import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JDesktopPane;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.WindowConstants;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeCellRenderer;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeModel;
import javax.swing.tree.TreeSelectionModel;


public class ClassWizard extends Object{
    public static void main(String args[]) throws Exception{
        try{
            DialogTest ket = new DialogTest();
            GJApp.launch(ket, " TreeTest " ,0,0,700,700,null);
        }
        catch (Exception e){
            System.out.println(e.getMessage());
            e.printStackTrace();
        }
    }
}
class GJApp extends WindowAdapter{
    public static void launch(final DialogTest f, String title,final int x, final int y,final int w, int h,String propertiesFilename){
        f.setTitle(title);
        f.setBounds(x,y,w,h);
        f.setVisible(true);
        f.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
        f.addWindowListener(new WindowAdapter(){
            public void windowClosed(WindowEvent e){
                System.exit(0);
            }
        });
    }
}

class DialogTest extends JFrame{
    protected JDesktopPane desktopPane = new JDesktopPane();
    CustomerJTree _tree = null;
    DefaultTreeModel _treeModel = null;
    TreeDialog _treedlg = null;
    
    public DialogTest() throws Exception{
        String osname = System.getProperty( " os.name " );
        String osversion = System.getProperty( " os.version " );
        String java_version = System.getProperty( " java.version " );
        System.out.println(osname + " " + osversion + " java: " + java_version + "
 " );
        
        // make a tree
        DefaultMutableTreeNode root = new DefaultMutableTreeNode( " root " );
        _treeModel = new DefaultTreeModel(root);
        for(int i=0; i< 15; i++){
            DefaultMutableTreeNode nodex = new DefaultMutableTreeNode( " node " + i);
            _treeModel.insertNodeInto(nodex, root, root.getChildCount());
        }
         _tree = new CustomerJTree(_treeModel,this);
        
        // make a dialog for the tree
        _treedlg = new TreeDialog( " tree " ,false,this);
        _treedlg.init(_tree);
        _treedlg.setVisible(true);
        _treedlg.setLocation(100, 100);
    }
}

class CustomerJTree extends JTree{
    DialogTest _owner = null;
    
    public CustomerJTree(TreeModel newModel,DialogTest owner){
        super(newModel);
        _owner = owner;
    }
}
class TreeDialog extends JDialog{
    DialogTest _owner = null;
    TreeDialog _dialog = this;
    JTree _tree = null;
    public TreeDialog(String title, boolean modal,DialogTest owner){
        super(owner,title,modal);
        _owner = owner;
    }
    
    private JPanel getNewTabPanel(JTree tree){
        JPanel panel = new JPanel(new BorderLayout(0, 0));
        if(tree != null){
            JScrollPane spane = new JScrollPane(
                tree,
                JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
                JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
            panel.add(spane, BorderLayout.CENTER);
        }
        return panel;
    }

    public void init(JTree tree){
        try{
            tree.setCellRenderer(new DefaultTreeCellRenderer());
            _tree = tree;
            TreeSelectionModel model = tree.getSelectionModel();
            model.setSelectionMode(TreeSelectionModel.DISCONTIGUOUS_TREE_SELECTION);
            _tree.putClientProperty( " JTree.lineStyle " , " Angled " );
            Container diacontent = this.getContentPane();
            diacontent.setLayout(new BorderLayout(0, 0));
            JPanel paraPanel = getNewTabPanel(tree);
            diacontent.add(paraPanel, BorderLayout.CENTER);
        }
        catch (Exception ex){
            System.out.println(ex.getMessage());
            ex.printStackTrace();
        }
        setPreferredSize(new Dimension(100, 300));
        setResizable(true);
        pack();
    }
}

---------- END SOURCE ----------