RFR: JDK-8322795 CSS performance regression up to 10x

[John Hendrikx]

On Wed, 3 Jan 2024 18:33:29 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> The regression is caused by the `Collections.unmodifiableSet` wrapper not being recognized by `BitSet`, and a fall back is done to a less optimized version of `containsAll`.
>> 
>> As this is a regression fix, I've kept the fix as small as reasonable.  I'll provide a further optimized version as part of https://bugs.openjdk.org/browse/JDK-8322964 which eliminates the need for `BitSet` and `StyleClass` in the hot code paths which should result in a further CSS performance improvement.
>> 
>> I've tested this solution with the JFXCentral application locally and the regression seems resolved.
>
>> As this is a regression fix, I've kept the fix as small as reasonable
> 
> Thanks. That seems like the best solution.

@kevinrushforth should this perhaps be backported to 21?

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PR Comment: https://git.openjdk.org/jfx/pull/1314#issuecomment-1986992136