RFR: JDK-8225013: sanity/client/SwingSet/src/ScrollPaneDemoTest.java fails on Linux [v2]

[Phil Race]

On Mon, 23 May 2022 18:00:39 GMT, Alexandre Iline <shurailine at openjdk.org> wrote:

>> Before the fix the test was failing around 1 time in fifty runs. After the fix the test did not fail in ~ 1k runs.
>> Additional instrumentation is added to save useful information on the UI state, should the failure happen again.
>
> Alexandre Iline has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Using modern language features.

Marked as reviewed by prr (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/8848