[jdk16u] RFR: 8262446: DragAndDrop hangs on Windows

[Dmitry Markov]

Clean back port of bf9b74d18767619f0765ed1435e35e28077a4220

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Commit messages:
 - 8262446: DragAndDrop hangs on Windows

Changes: https://git.openjdk.java.net/jdk16u/pull/82/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk16u&pr=82&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8262446
  Stats: 8 lines in 1 file changed: 7 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk16u/pull/82.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16u pull/82/head:pull/82

PR: https://git.openjdk.java.net/jdk16u/pull/82