RFR: JDK-8304960: ObservableListBase should defer constructing ListChangeBuilder

Wed Mar 29 12:20:38 UTC 2023

A 1200 Node application sees a 2/3rds reduction of ListChangeBuilder's created.  Every `Node` for example has an `ObservableList` for style classes, and every `Parent` has one for stylesheets, which rarely if ever change.

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Commit messages:
 - Defer initialization of ListChangeBuilder in ObservableListBase

Changes: https://git.openjdk.org/jfx/pull/1075/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1075&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8304960
  Stats: 18 lines in 1 file changed: 8 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jfx/pull/1075.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1075/head:pull/1075

PR: https://git.openjdk.org/jfx/pull/1075