RFR: 8257719: JFXPanel scene fails to render correctly on HiDPI after fix for JDK-8199592 [v3]

[Kevin Rushforth]

On Wed, 9 Dec 2020 15:36:19 GMT, Jose Pereda <jpereda at openjdk.org> wrote:

>> This PR fixes a regression introduced in [JDK-8199592](https://bugs.openjdk.java.net/browse/JDK-8199592), where scene initialization was moved after updating output scales. However, in case of embedded windows (used by `JFXPanel` or `FXCanvas`), the scene has to be initialized before.
>> 
>> A test has been included. Before applying the fix, the JFXPanel is rendered with a garbled image, and after the fix, the rendering is correct.
>
> Jose Pereda has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add comment to test

Marked as reviewed by kcr (Lead).

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PR: https://git.openjdk.java.net/jfx/pull/364