RFR: 8246745: ListCell/Skin: misbehavior on switching skin [v2]

[Jeanette Winzenburg]

> ListCellSkin installs listeners to the ListView/fixedCellSize that introduce a memory leak, NPE on replacing the
> listView and incorrect update of internal state (see bug report for details)
> Fixed by removing the listeners (and the internal state had been copied from listView on change) and access of listView
> state when needed.
> Added tests that failed before and pass after the fix, plus a sanity test to guarantee same (correct) behavior
> before/after.

Jeanette Winzenburg has updated the pull request incrementally with one additional commit since the last revision:

  added code comment as requested in review

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

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/251/files
  - new: https://git.openjdk.java.net/jfx/pull/251/files/c21ed224..75c209a3

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=251&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=251&range=00-01

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/251.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/251/head:pull/251

PR: https://git.openjdk.java.net/jfx/pull/251