RFR: 8252936: Optimize removal of listeners from ExpressionHelper.Generic

[yosbits]

On Thu, 1 Apr 2021 23:50:12 GMT, Marius Hanl <github.com+66004280+Maran23 at openjdk.org> wrote:

>> Because it is such a small correction
>> Problem from me I feel that it is not easy to register, but I will try to register. 
>> 
>> It has passed two existing tests for compatibility:
>> 
>> * gradle base:test 
>> * gradle controls:test 
>> 
>> I have just reported it as an enhancement proposal.
>
> Any news for this PR? Can I help somewhere?

It seems that performance improvement PR often needs to make up for the lack of existing unit tests. However, this addition of unit tests should not be included in the same PR as it needs to be tested to meet the specifications before and after the change.

**I think we need a step to fix the lack of unit tests before the performance improvement patch.**

And care must be taken not to rely on internal implementations for this unit test so as not to hinder performance improvement. Some existing unit test code depends on the internal implementation, so some test changes may be needed.

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PR: https://git.openjdk.java.net/jfx/pull/108