RFR: JDK-8354340 : Open source Swing Tests - Set 6

[Harshitha Onkar]

Following tests are open-sourced in this PR:

- javax/swing/JViewport/ScrollRectToVisibleTest3.java - automated
- javax/swing/JViewport/SetViewRepaint.java - manual

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Commit messages:
 - swing tests set6

Changes: https://git.openjdk.org/jdk/pull/24697/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24697&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8354340
  Stats: 280 lines in 2 files changed: 280 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24697.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24697/head:pull/24697

PR: https://git.openjdk.org/jdk/pull/24697