RFR: 8327478: Add System test to verify TextSelection issue for webkit-617.1 [v3]

[Gopal Pattnaik]

On Wed, 5 Mar 2025 00:28:46 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> what if the lambdas never run?
>
> Then we have far bigger problems than this one test. The reason we use `runAndWait` instead of `runLater` is so we guarantee that the lambda has run before that method returns. It's guaranteed to do so.

Added volatile to the variables colorBefore and colorAfter.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1719#discussion_r1980814766