RFR: 8263322: Deadlock when calling Application.launch in the FXThread after Platform.startup [v2]

[Florian Kirmaier]

On Wed, 10 Mar 2021 16:42:41 GMT, Florian Kirmaier <fkirmaier at openjdk.org> wrote:

>> I forgot to commit a part of the fix, which is why the second test hang. It's now part of the PR.
>
> About the CSR:
> This commit actually restores original behavior, when JavaFX was called with Application.launch, so it's not really a change in the API, it's more like a fix for a regression.
> How would I create a CSR? Just by creating a ticket at https://bugs.openjdk.java.net/issues/?jql=issuetype%20%3D%20CSR with the type CSR?

`Initalize the FX runtime via Platform.startup and then launch an Application on another thread (should succeed)`
I don't think that should succeed. I would expect it to throw an exception. If that would be the case, then both startup-methods would result in different states, which wouldn't be so good.

I've now restructured the tests.
It's a total of 4 tests. 2 after Application.launch and 2 after Platform.startup. 
In both cases I check what happens, a Application is launched from another thread, or from the javafx thread. In all cases an exception is expected.

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PR: https://git.openjdk.java.net/jfx/pull/421