RFR: 8232824: Removing TabPane with strong referenced content causes memory leak from weak one

[Kevin Rushforth]

On Mon, 13 Jan 2020 16:49:41 GMT, Ambarish Rapte <arapte at openjdk.org> wrote:

>> This will need a second reviewer.
>> 
>> @aghaisas can you review this, too?
> 
>> 
>> 
>> @arapte - This bug looks like a good candidate for JavaFX 14. Can you retarget this PR to the jfx14 branch?
> 
> Thanks for guiding Kevin, PR is now targeted to jfx14.

The fix looks good. I'll take a closer look at the unit test later.

Speaking of tests...since the addition of the `TabPane` reordering logic was a victim of the already-existing leak in the `viewOrderChildren` list in `Parent`, it should be possible to write a test case using a Group node and a few Shape nodes, using setViewOrder directly on the Group node (this would be in addition to the system test you wrote). Can you take a look at adding one? It might even be possible to do it as a `javafx.graphics` module unit test rather than a system test, although you would need to see if the bug reproduced there (I suspect it will).

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PR: https://git.openjdk.java.net/jfx/pull/79