RFR: 8139173: [macosx] JInternalFrame shadow is not properly drawn [v2]

[Toshio Nakamura]

> JInternalFrame's bottom area is not properly drawn with Aqua LAF.
> This problem remained for long time, but we recognized it recently.
> 
> According to the bug report, it depends on MacOS's version. I don't have old ones (10.10 and 10.11 in the report), but the current MacOS can recreate the issue. I confirmed the following OS versions recreated this issue and this patch could solve it.
> 
> Mojave 10.14.6
> Catalina 10.15.7
> Big Sur 11.6.2
> Monterey 12.1
> 
> jtreg "javax/swing" and "java/awt" have no regression.

Toshio Nakamura has updated the pull request incrementally with one additional commit since the last revision:

  Applied review comments

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7228/files
  - new: https://git.openjdk.java.net/jdk/pull/7228/files/44ea0e12..422a9c33

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7228&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7228&range=00-01

  Stats: 27 lines in 2 files changed: 11 ins; 6 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7228.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7228/head:pull/7228

PR: https://git.openjdk.java.net/jdk/pull/7228