[jfx11u] RFR: 8263169: [macos] JavaFX windows open as tabs when system preference for documents is set

[Kevin Rushforth]

Clean backport of macOS tabbed windows fix. Verified on Mac (the fix is macOS-specific).

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Commit messages:
 - 8263169: [macos] JavaFX windows open as tabs when system preference for documents is set

Changes: https://git.openjdk.java.net/jfx11u/pull/5/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx11u&pr=5&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263169
  Stats: 174 lines in 2 files changed: 174 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx11u/pull/5.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx11u pull/5/head:pull/5

PR: https://git.openjdk.java.net/jfx11u/pull/5