[9] Review request for 8073453: Focus doesn't move when pressing Shift + Tab keys

[dmitry markov]

Hello,

Could you review the fix for jdk9, please?
    bug: https://bugs.openjdk.java.net/browse/JDK-8073453
    webrev: http://cr.openjdk.java.net/~dmarkov/8073453/jdk9/webrev.00/

Problem description:
The method ContainerOrderFocusTraversalPolicy.getLastComponent() always 
returns null if the last component is a container with focus traversal 
policy and does not have any sub-components. In some cases such 
behaviour of getLastComponent() causes failure during reverse focus 
transition, (i.e. focus stays on the selected component when SHIFT+TAB 
is pressed).

Fix:
If the last component is a container with focus traversal policy and 
does not have any sub-components, the method getLastComponent() should 
return a previous component instead of null.
Please note: the same approach is already implemented for 
ContainerOrderFocusTraversalPolicy.getFirstComponent().

Thanks,
Dmitry