RFR: 8319341: [Linux] Remove operation to show or hide children because it is unnecessary

Thu Nov 2 20:05:24 UTC 2023

Observed that the window manager takes care of showing and hiding children because we set `gtk_window_set_transient_for`.

Works since Ubuntu 16.04.

This PR removes the code to show or hide children because it "duplicates" the operation and might lead to unknown bugs.

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Commit messages:
 - Remove show or hide children

Changes: https://git.openjdk.org/jfx/pull/1279/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1279&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319341
  Stats: 31 lines in 4 files changed: 0 ins; 31 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1279.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1279/head:pull/1279

PR: https://git.openjdk.org/jfx/pull/1279