[jfx11u] RFR: 8278759: PointerEvent: buttons property set to 0 when mouse down

[Ambarish Rapte]

Reviewed-by: kcr, arapte

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Commit messages:
 - 8278759: PointerEvent: buttons property set to 0 when mouse down

Changes: https://git.openjdk.java.net/jfx11u/pull/87/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx11u&pr=87&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8278759
  Stats: 302 lines in 8 files changed: 293 ins; 1 del; 8 mod
  Patch: https://git.openjdk.java.net/jfx11u/pull/87.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx11u pull/87/head:pull/87

PR: https://git.openjdk.java.net/jfx11u/pull/87