RFR: 8263322: Calling Application.launch on FX thread should throw IllegalStateException, but causes deadlock [v8]

[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
  Various changes based on code-review

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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/a73bcf82..2b275f55

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=421&range=07
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=421&range=06-07

  Stats: 21 lines in 7 files changed: 2 ins; 17 del; 2 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