RFR: 8190264: JScrollBar ignores its border when using macOS Mac OS X Aqua look and feel [v3]

[Alisen Chung]

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

Alisen Chung has updated the pull request incrementally with two additional commits since the last revision:

 - removed trailing whitespace
 - test change

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6374/files
  - new: https://git.openjdk.java.net/jdk/pull/6374/files/40157e04..e6dab9b2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6374&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6374&range=01-02

  Stats: 196 lines in 1 file changed: 0 ins; 0 del; 196 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