RFR: 8325564: ComboBox popup does not correctly resize after update when on display [v4]

[Ziad El Midaoui]

> Fixed popup size not changing to show more items or less when changing the number of items in `ComboBox` by adding a `popupResize` variable which triggers a request layout when there is change in items list.
> Tested with the test app in bug and MonkeyTester.

Ziad El Midaoui has updated the pull request incrementally with one additional commit since the last revision:

  Fix scrollbar issue

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Changes:
  - all: https://git.openjdk.org/jfx/pull/2052/files
  - new: https://git.openjdk.org/jfx/pull/2052/files/29a4d177..9ed0cee1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=2052&range=03
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=2052&range=02-03

  Stats: 25 lines in 2 files changed: 20 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jfx/pull/2052.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/2052/head:pull/2052

PR: https://git.openjdk.org/jfx/pull/2052