8295242: ScrollBarSkin: memory leak when changing skin

[andy-goryachev-oracle]

Fixed memory leak when changing skin in ScrollBarSkin (was adding an event handler without removing it in dispose()).

This change depends on ListenerHelper PR
#908

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Progress

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Issue

• JDK-8295242: ScrollBarSkin: memory leak when changing skin

Reviewing

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[bridgekeeper]

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[openjdk]

⚠️ @andy-goryachev-oracle This pull request contains merges that bring in commits not present in the target repository. Since this is not a "merge style" pull request, these changes will be squashed when this pull request in integrated. If this is your intention, then please ignore this message. If you want to preserve the commit structure, you must change the title of this pull request to Merge <project>:<branch> where <project> is the name of another project in the OpenJDK organization (for example Merge jdk:master).

[mlbridge]

Webrevs

• 00: Full (dd27e686)

[andy-goryachev-oracle]

changes will be reviewed as a part of #928