RFR: 8201567: QuantumRenderer modifies buffer in use by JavaFX Application Thread [v2]

[Kevin Rushforth]

On Wed, 8 Jul 2020 22:02:17 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> @jgneff this looks safe enough to get into 15. Go ahead an retarget it to the `jfx15` branch.
>> 
>> @arapte this will invalidate your review, so you will need to re-review it once retargeted.
>
> Oh, and regarding the following:
> 
>> JavaFX on macOS prints the error shown below when Platform.exit is called to end the application.
> 
> That's a known issue on macOS 10.15:
> 
> [JDK-8231558](https://bugs.openjdk.java.net/browse/JDK-8231558): [macos 10.15] Platform.exit causes assertion error on
> macOS Catalina

I am done with my testing. All looks good. Once this PR is retargeted to `jfx15` I will approve it.

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PR: https://git.openjdk.java.net/jfx/pull/255