RFR: JDK-8202790: DnD test DisposeFrameOnDragTest.java does not clean up [v2]

[Phil Race]

On Mon, 25 Apr 2022 21:46:27 GMT, Alisen Chung <achung at openjdk.org> wrote:

>> Added a background to the test to prevent the file from dragging onto the desktop and creating an extra file.
>
> Alisen Chung has updated the pull request incrementally with one additional commit since the last revision:
> 
>   changed button mask to button down mask

Marked as reviewed by prr (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/8370