RFR: 8326712: Robot tests fail on XWayland [v2]

[Alexander Zvegintsev]

On Fri, 28 Jun 2024 13:52:10 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> Johan makes a good point, so go ahead and add it back.
>
> Worth noting is that this `HEADLESS` check is just an assertion to verify that the build logic properly excludes the file from the build when building headless. It otherwise does nothing.

The `HEADLESS` check is back.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1490#discussion_r1659138998