RFR: 8263322: Deadlock when calling Application.launch in the FXThread after Platform.startup [v4]

[Florian Kirmaier]

> Fixing deadlock when calling Application.launch in the FXThread after Platform.startup

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

  JDK-8263322
  updated the javadoc to mention the new case.

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Changes:
  - all: https://git.openjdk.java.net/jfx/pull/421/files
  - new: https://git.openjdk.java.net/jfx/pull/421/files/0abc71e0..c16b6067

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=421&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=421&range=02-03

  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/421.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/421/head:pull/421

PR: https://git.openjdk.java.net/jfx/pull/421