[Rev 01] RFR: 8220722: ProgressBarSkin: adds strong listener to control's width property

[Jeanette Winzenburg]

The pull request has been updated with a complete new set of changes (possibly due to a rebase).

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Commits:
 - a4fae9d7: 8220722: ProgressBarSkin: adds strong listener to control's width

Changes: https://git.openjdk.java.net/jfx/pull/59/files
 Webrev: https://webrevs.openjdk.java.net/jfx/59/webrev.01
  Issue: https://bugs.openjdk.java.net/browse/JDK-8220722
  Stats: 93 lines in 2 files changed: 88 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jfx/pull/59.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/59/head:pull/59

PR: https://git.openjdk.java.net/jfx/pull/59