[jfx15] RFR: 8248381: Create a daemon thread for MonocleTimer [v2]

[Johan Vos]

On Sun, 28 Jun 2020 02:28:35 GMT, John Neffenger <github.com+1413266+jgneff at openjdk.org> wrote:

>> Fixes [JDK-8248381](https://bugs.openjdk.java.net/browse/JDK-8248381).
>
> John Neffenger has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove POOL_SIZE constant

I'm ok with this, as it fixes regression.
A longer-term requirement could be the addition of platform-independent start/stop and pause/resume methods, similar to
http://hg.openjdk.java.net/openjfx/jfx-dev/rt/rev/4e1e2f56c7af (https://bugs.openjdk.java.net/browse/JDK-8189926)

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Marked as reviewed by jvos (Reviewer).

PR: https://git.openjdk.java.net/jfx/pull/256