PIT : List is not rendered correctly if JScrollPane scrollbar is moved

I have added few AWT & Swing Components into the JScrollPane. When the frame is realized , o try to navigate the JScrollPane by clicking on the horizontal scrollbar arrow button. I see that AWT List is not fully rendered. This was working fine in 6u12 b02 promoted build. But now in 6u12 b03 pit build its AWT List is not fully rendered. Hence its a regression introduced in this pit build.
Workaround for this issue is . I need to minimize the frame & restore to see the AWT List. Even same for the AWT Checkbox which is next to AWTList.

I have attached the screen shot of the same.

Step to reproduced:-
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1) Run the attached testcase.
2) Click on the horizontal scrollbar of the JScrollPane. Observe that AWTList is not fully rendered . If you see the same then the bug is not reproduced.