RFR: 8274929: Crash while reading specific clipboard content [v2]

[Kevin Rushforth]

> This bug is caused by not sanity checking the data returned by a call to the Windows Clipboard `IDataObject::GetData` method. When requesting a file descriptor with a format of either `CFSTR_FILEDESCRIPTORA` or `CFSTR_FILEDESCRIPTORW`, which returns a list of file names, the first word of the returned data buffer is supposed to be the number of items that follow. Applications can put data on the clipboard in such a way that it will respond to a request to return the list of files from the clipboard with data that isn't formatted correctly, so we can't assume that the first word is a valid count.
> 
> The fix is to check the returned buffer size against the item count. I added a regression test that fails before and passes after the fix.

Kevin Rushforth has updated the pull request incrementally with one additional commit since the last revision:

  Update check to test that bufferSize is exactly the right size

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Changes:
  - all: https://git.openjdk.java.net/jfx/pull/662/files
  - new: https://git.openjdk.java.net/jfx/pull/662/files/abcd51c4..ff5f9c1a

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=662&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=662&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jfx/pull/662.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/662/head:pull/662

PR: https://git.openjdk.java.net/jfx/pull/662