RFR: 8271395: Fixing crash at printing [v2]

[Florian Kirmaier]

> This PR switches the Thread to the QuantumRenderer, in the case the Disposer is called from another Thread - the printing Thread.
> I'm open for better solutions on how to fix this Issue.
> Initially i thought there is also a Race Condition in the resource pool, but a new one is created for the Printing Thread.

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

  JDK-8271395
  QuantumRenderer is no longer public

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Changes:
  - all: https://git.openjdk.java.net/jfx/pull/618/files
  - new: https://git.openjdk.java.net/jfx/pull/618/files/72f9f9f1..0dc9ce1d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=618&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=618&range=00-01

  Stats: 27 lines in 3 files changed: 15 ins; 10 del; 2 mod
  Patch: https://git.openjdk.java.net/jfx/pull/618.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/618/head:pull/618

PR: https://git.openjdk.java.net/jfx/pull/618