RFR: 8263807: Button types of a DialogPane are set twice, returns a wrong button [v2]

[Marius Hanl]

> When DialogPane#getButtonTypes().setAll() is called twice with the same argument(s), DialogPane#lookupButton does not return the node which is shown inside the button bar.
> This is due DialogPane adding two list change listeners to 'buttons' (#getButtonTypes). They have the wrong order, which will result in the button bar not changing at all and the 'buttonNodes' list will recreate the dialog button(s).
> Finally, this will make DialogPane#lookupButton returning the 'wrong' button, which is in fact not used inside the dialog button bar.

Marius Hanl has updated the pull request incrementally with one additional commit since the last revision:

  8263807: Code review changes

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Changes:
  - all: https://git.openjdk.java.net/jfx/pull/432/files
  - new: https://git.openjdk.java.net/jfx/pull/432/files/f3dd7a2a..dc65db19

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=432&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=432&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jfx/pull/432.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/432/head:pull/432

PR: https://git.openjdk.java.net/jfx/pull/432