RFR: 8269907 memory leak - Dirty Nodes / Parent removed [v10]

[Florian Kirmaier]

> After thinking about this issue for some time, I've now got a solution.
> I know put the scene in the state it is, before is was shown, when the dirtyNodes are unset, the whole scene is basically considered dirty. 
> This has the drawback of rerendering, whenever a window is "reshown", but it restores sanity about memory behaviour, which should be considered more important.

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

  JDK-8269907
  more changes based on codereview

-------------

Changes:
  - all: https://git.openjdk.org/jfx/pull/584/files
  - new: https://git.openjdk.org/jfx/pull/584/files/dfb34701..e8e2f592

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=584&range=09
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=584&range=08-09

  Stats: 8 lines in 2 files changed: 3 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jfx/pull/584.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/584/head:pull/584

PR: https://git.openjdk.org/jfx/pull/584