RFR: 8252236: TabPane: must keep header of selected tab visible [v3]

[Ambarish Rapte]

On Thu, 24 Sep 2020 13:10:41 GMT, Jeanette Winzenburg <fastegal at openjdk.org> wrote:

>> the issue is that the header of the selected tab is not always visible (or kept visible, see report for details)
>> 
>> - initially
>> - after changing side
>> - after resizing stage/tabPane
>> - after modifying the list of tabs
>> 
>> Fixed in TabPaneSkin to notify its TabHeaderArea (== collaborator that is responsible for layout the tabs) whenever its
>> scroll might need an update.
>> Added tests that fail before and pass after the fix.
>> 
>> Note that there still are issues while/after dragging, which are separated into
>> [JDK-8253352](https://bugs.openjdk.java.net/browse/JDK-8253352)
>
> Jeanette Winzenburg has updated the pull request incrementally with one additional commit since the last revision:
> 
>   removed empty else-block and added code comment

Looks good to me.

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Marked as reviewed by arapte (Reviewer).

PR: https://git.openjdk.java.net/jfx/pull/300