RFR: 8324658: Allow animation play/start/stop/pause methods to be called on any thread [v5]

[Kevin Rushforth]

On Sat, 27 Jan 2024 18:27:21 GMT, Nir Lisker <nlisker at openjdk.org> wrote:

> The API looks good now...

As for the implementation, the only two things I see that are needed are:
1. Move the checks for `parent != null ` back to the original methods (i.e., before delegating). Without this, we are not conforming the spec of the `@throws` clause, since the exception isn't thrown back to the caller.
2. Fix or remove the failing system test. Unless you add it as part of this PR, I recommend filing a follow-up issue to add a system test based on the failing test program that is attached to [JDK-8159048](https://bugs.openjdk.org/browse/JDK-8159048).

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PR Comment: https://git.openjdk.org/jfx/pull/1352#issuecomment-1913290372