<AWT Dev> RFR: 8262446: DragAndDrop hangs on Windows [v4]

[Dmitry Markov]

> The IME functions and the DND operation must be executed on the toolkit thread. If the DND operation is in progress, the IME API is invoked via SendMessage() call inside InvokeInputMethodFunction() to avoid a hang. The flag isInDoDragDropLoop indicates whether the DND takes place or not. The flag works properly if the DND is performed between two Java windows. However if anything is dragged from native app, (e.g. Windows FileExplorer) to Java the flag is NOT set. That’s the root cause of the hang.
> 
> Fix:
> Introduce a new flag to indicate DND operation between Java and native app. 
> 
> Testing:
> mach5 green

Dmitry Markov has updated the pull request incrementally with one additional commit since the last revision:

  Update copyright

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2825/files
  - new: https://git.openjdk.java.net/jdk/pull/2825/files/dbc9dac7..3810f1b0

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2825&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2825&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2825.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2825/head:pull/2825

PR: https://git.openjdk.java.net/jdk/pull/2825