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

[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.

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Commit messages:
 - Merge branch 'openjdk:master' into 8325564.popupSize
 - Merge branch 'openjdk:master' into 8325564.popupSize
 - Fixed ComboBox popup size not changing after update.

Changes: https://git.openjdk.org/jfx/pull/2052/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=2052&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325564
  Stats: 22 lines in 2 files changed: 19 ins; 0 del; 3 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