RFR: 7124282: [macosx] Can't see table cell highlighter when the highlight border is the same color as the cell.

[Harshitha Onkar]

Previously while tabbing through the JTable cell, the cell highlighter/focus ring was not visible against the selection background. 

Changes were made to Aqua LAF to derive a brighter focus ring color by changing hue, saturation and brightness of selection background color so that it is visible while tabbing through JTable cells. 

A test case is added to compare the RGB difference between the original focus ring color & selection background and the brighter focus ring color & selection background.

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Commit messages:
 - Cell Focus Ring Changes for Aqua LAF

Changes: https://git.openjdk.java.net/jdk/pull/7768/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7768&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-7124282
  Stats: 197 lines in 2 files changed: 195 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7768.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7768/head:pull/7768

PR: https://git.openjdk.java.net/jdk/pull/7768