JInternalFrame background color seems to overflow into the border region. This issue is more prominently seen on Windows - Metal LAF (with fractional scaling, as show below). The primary reason is border scaling issue as observed in - [JDK-8279614](https://bugs.openjdk.org/browse/JDK-8279614) & [JDK-8282958](https://bugs.openjdk.org/browse/JDK-8282958)
The fix involves a similar approach as described here https://github.com/openjdk/jdk/pull/7449#issuecomment-1068218648. The test checks the midpoint and corners of borders to check if the internal frame's background color is located out of JInternalFrame.  ------------- Commit messages: - added test summary - updated test case - Added test case, minor position changes to shadow lines - expanded imports - JIF Metal Border Scaling - Initial changes Changes: https://git.openjdk.org/jdk/pull/10274/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10274&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8015739 Stats: 402 lines in 2 files changed: 354 ins; 5 del; 43 mod Patch: https://git.openjdk.org/jdk/pull/10274.diff Fetch: git fetch https://git.openjdk.org/jdk pull/10274/head:pull/10274 PR: https://git.openjdk.org/jdk/pull/10274
