[Rev 01] RFR: 8245282: Button/Combo Behavior: memory leak on dispose

[Jeanette Winzenburg]

> Reason for the memory leak is a listener on control's focusProperty that is not correctly removed on dispose. For
> details please see the report.
> Added a test method to ButtonSkinTest that failed before and passes after the fix.

Jeanette Winzenburg has updated the pull request with a new target base due to a merge or a rebase. The pull request
now contains one commit:

  8245282: Button/Combo Behavior: memory leak on dispose

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Changes: https://git.openjdk.java.net/jfx/pull/226/files
 Webrev: https://webrevs.openjdk.java.net/jfx/226/webrev.01
  Stats: 45 lines in 3 files changed: 8 ins; 33 del; 4 mod
  Patch: https://git.openjdk.java.net/jfx/pull/226.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/226/head:pull/226

PR: https://git.openjdk.java.net/jfx/pull/226