[jdk17u-dev] RFR: 8015739: Background of JInternalFrame is located out of JInternalFrame

[Goetz Lindenmaier]

I backport this for parity with 17.0.12-oracle.

Resolved Copyright, will mark clean if needed.

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Commit messages:
 - Backport f857f795a9fc8b116bfc6b039114051061950e28

Changes: https://git.openjdk.org/jdk17u-dev/pull/2301/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2301&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8015739
  Stats: 408 lines in 2 files changed: 360 ins; 8 del; 40 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/2301.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/2301/head:pull/2301

PR: https://git.openjdk.org/jdk17u-dev/pull/2301