<Swing Dev> Accessibility inner classes in AccessibleJTable do not stick to AccessibleComponent.getLocationOnScreen api

[Frank Ding]

Hi guys
   According to javadoc of AccessibleComponent.getLocationOnScreen, it 
returns null instead of throwing IllegalComponentStateException when the 
corresponding GUI object is not visible.
   However, two accessibility inner classes of JTable, 
JTable$AccessibleJTable$AccessibleJTableCell and 
Table$AccessibleJTable$AccessibleJTableHeaderCell implementing 
AccessibleComponent throw IllegalComponentStateException when the 
corresponding JTable is not visible.  This behavior conflicts with the spec.
   I have submitted a bug in sunbug system reporting the issue, and 
received two acknowledgement emails (bug id 7188613 and 7188612, don't 
know why there are two?).  I created a patch to fix the issue with a 
jtreg test case.  Both the patch and the test are uploaded into the 
following space.

http://cr.openjdk.java.net/~youdwei/ojdk-491/webrev.02/

   Would anyone help to review the patch?

Best regards,
Frank