RFR: 8206430: Use consistent pattern for startup in FX system tests

[Andy Goryachev]

On Wed, 16 Nov 2022 08:27:17 GMT, Ajit Ghaisas <aghaisas at openjdk.org> wrote:

> This is resulting in two test failures when run as a FULL system test run on my macBook with macOS 11.7.1.
> 
> * test.javafx.scene.web.ColorChooserTest.testColorChooser()
> * test.robot.javafx.scene.ComboBoxTest.testComboBoxSceneChange1()

This is weird, I'll definitely take a look.
On my Mac M1 I do get occasional failure in [StraightLineTest](https://github.com/openjdk/jfx/pull/classes/test.javafx.scene.web.StraightLineTest.html). [testLine](https://github.com/openjdk/jfx/pull/classes/test.javafx.scene.web.StraightLineTest.html#testLine) when running with no debug output.

I am running the full test with this command - am I missing anything?

-------------

PR: https://git.openjdk.org/jfx/pull/950