RFR: 8361524: [XWayland] possible JavaFX interop hang

[Alexander Zvegintsev]

Callbacks in the `src/java.desktop/unix/native/libawt_xawt/awt/screencast_portal.c` file normally have the following pattern:


helper->isDone = TRUE;
callbackEnd();
// return;


Failing to call `callbackEnd()` could result in a hang if another GTK loop is running (e.g., JavaFX see https://github.com/openjdk/jdk/pull/22131#issue-2660482472).

This fix corrects this flaw.

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Commit messages:
 - 8361524: [XWayland] possible JavaFX interop hang

Changes: https://git.openjdk.org/jdk/pull/26172/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26172&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361524
  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/26172.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26172/head:pull/26172

PR: https://git.openjdk.org/jdk/pull/26172