<Swing Dev> RFR: 8075915: The eight controls without black backgrounds with WinLAF & GTK LAF & Nimbus LAF

[Alexander Zvegintsev]

This manual test was written for Metal L&F, so now it is set explicitly.
Test is also refactored to use JFrame instead of Applet.

The test is not in `ProblemList.txt`.
It still fails on JDK 1.5 (after removing all syntactic sugar).

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Commit messages:
 - trailing whitespaces fix
 - instructions update
 - initial

Changes: https://git.openjdk.java.net/jdk/pull/3474/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3474&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8075915
  Stats: 187 lines in 2 files changed: 77 ins; 63 del; 47 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3474.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3474/head:pull/3474

PR: https://git.openjdk.java.net/jdk/pull/3474