RFR: 8190264: JScrollBar ignores its border when using macOS Mac OS X Aqua look and feel

[Alisen Chung]

Adjusted the AquaLF scrollbar to account for border inset settings when dragging the thumb and clicking on the track.

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Commit messages:
 - 8190264: JScrollBar ignores its border when using macOS Mac OS X Aqua look and feel

Changes: https://git.openjdk.java.net/jdk/pull/6374/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6374&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8190264
  Stats: 17 lines in 1 file changed: 11 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6374.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6374/head:pull/6374

PR: https://git.openjdk.java.net/jdk/pull/6374