RFR: 8189354: Change.getRemoved() list contains incorrect selected items when a TreeItem is collapsed [v9]

[Ambarish Rapte]

On Mon, 3 May 2021 20:51:13 GMT, mstr2 <github.com+43553916+mstr2 at openjdk.org> wrote:

>> This PR fixes the implementation of `ControlUtils.reducingChange`, which incorrectly computed adjacent removed indices, thus resulting in incorrect removal notifications.
>> 
>> Since there were no unit tests for this method, I also added a bunch of tests.
>> 
>> After applying this fix, I can no longer reproduce [JDK-8189354](https://bugs.openjdk.java.net/browse/JDK-8189354) and [JDK-8189228](https://bugs.openjdk.java.net/browse/JDK-8189228).
>
> mstr2 has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Rename local variable in test
>  - Remove unrelated fix

looks good to me.

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Marked as reviewed by arapte (Reviewer).

PR: https://git.openjdk.java.net/jfx/pull/480