<Swing Dev> RFR: 8058704: Nimbus does not honor JTextPane background color [v4]

[Prasanta Sadhukhan]

> The Nimbus look and feel ignores the configured background color of a JTextPane and always uses white. 
> Every other look and feel tested (Metal, Motif, and Windows) correctly honors the configured background color of a JTextPane.
> Issue seems to be in the hardcoded background color in nimbus skin which is rectified via the fix. 
> After this fix, the background color is correctly updated to whatever is being set via JTextPane.setBackground().
> 
> CI all test run is green.

Prasanta Sadhukhan has updated the pull request incrementally with two additional commits since the last revision:

 - Fix
 - Merge test

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4930/files
  - new: https://git.openjdk.java.net/jdk/pull/4930/files/f308e231..8e01458d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4930&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4930&range=02-03

  Stats: 309 lines in 3 files changed: 135 ins; 174 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4930.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4930/head:pull/4930

PR: https://git.openjdk.java.net/jdk/pull/4930