RFR: 8348100: Tooltips cannot be instantiated on background thread [v2]

[Andy Goryachev]

> Navigating up the parent hierarchy during CSS processing in a background thread encounters a null parent, causing a NPE.

Andy Goryachev has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 18 commits:

 - Merge branch 'master' into 8348100.tootlip.thread.safety
 - Merge remote-tracking branch 'origin/master' into 8348100.tootlip.thread.safety
 - cleanup
 - tooltip test
 - Merge branch '8348423.node.thread.safety' into 8348100.tootlip.thread.safety
 - Merge remote-tracking branch 'origin/master' into 8348423.node.thread.safety
 - skip tests
 - jiggler
 - tooltip test
 - better name
 - ... and 8 more: https://git.openjdk.org/jfx/compare/2cf9779b...3ba9c9a2

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Changes: https://git.openjdk.org/jfx/pull/1696/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1696&range=01
  Stats: 51 lines in 2 files changed: 46 ins; 1 del; 4 mod
  Patch: https://git.openjdk.org/jfx/pull/1696.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1696/head:pull/1696

PR: https://git.openjdk.org/jfx/pull/1696