RFR: 8264677 MemoryLeak: Progressindicator leaks, when treeShowing is false [v3]

[Florian Kirmaier]

> Fixing leak in ProgressIndicator when treeShowing is false

Florian Kirmaier has updated the pull request incrementally with one additional commit since the last revision:

  8264677
  Updated naming of the test,
  reworked the old test. It now has a much smaller scope and is easier to reason about, the initialization of JavaFX is now seperated from the test itself.

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Changes:
  - all: https://git.openjdk.java.net/jfx/pull/455/files
  - new: https://git.openjdk.java.net/jfx/pull/455/files/1a49a354..15fae375

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=455&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=455&range=01-02

  Stats: 51 lines in 1 file changed: 18 ins; 27 del; 6 mod
  Patch: https://git.openjdk.java.net/jfx/pull/455.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/455/head:pull/455

PR: https://git.openjdk.java.net/jfx/pull/455