RFR: JDK-8297449: Update JInternalFrame Metal Border code [v5]

[Alexey Ivanov]

On Thu, 1 Dec 2022 18:15:04 GMT, Harshitha Onkar <honkar at openjdk.org> wrote:

>> Updated Metal Border code for JInternalFrame. 
>> 
>> - Added instanceof check before casting Graphics to G2D.
>> - Replaced roundHalfDown with Region.clipRound()
>
> Harshitha Onkar has updated the pull request incrementally with one additional commit since the last revision:
> 
>   minor change

Marked as reviewed by aivanov (Reviewer).

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PR: https://git.openjdk.org/jdk/pull/11305