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

[dannygonzalez]

On Tue, 8 Sep 2020 20:14:48 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> I have attached a code sample. If you use OpenJFX 16-ea+1 and run visual VM and look at the hotspots in the JavaFX thread, you can see that about 45% of the time in the JavaFX thread is spent in removeListener calls.
>> 
>> Note: In CPU settings of VisualVM, I removed all packages from the "Do not profile packages section".
>> 
>> [JavaFXSluggish.java.zip](https://github.com/openjdk/jfx/files/5130298/JavaFXSluggish.java.zip)
>
> @dannygonzalez Per [this message](https://mail.openjdk.java.net/pipermail/openjfx-dev/2020-September/027534.html) on the openjfx-dev mailing list, I have filed a new JBS issue for this PR to use. Please change the title to:
> 
> 8252936: Optimize removal of listeners from ExpressionHelper.Generic

Thanks @kevinrushforth, I've changed the title.

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