RFR: 8377189: Intermittent failure in TooltipTest.testCssStylesheetChangeTooltip [v2]

[Michael Strauß]

> `test.robot.javafx.scene.TooltipTest` modifies the scene graph on a test worker thread, which can corrupt the scene graph and leads to test failures such as:
> 
> 
> TooltipTest > testCssStylesheetChangeTooltip() FAILED
>     java.lang.AssertionError
>         at [javafx.graphics at 27-ea](mailto:javafx.graphics at 27-ea)/com.sun.javafx.css.StyleMap.getCascadingStyles(StyleMap.java:144)
>         at [javafx.graphics at 27-ea](mailto:javafx.graphics at 27-ea)/javafx.scene.CssStyleHelper.resetToInitialValues(CssStyleHelper.java:490)
>         at [javafx.graphics at 27-ea](mailto:javafx.graphics at 27-ea)/javafx.scene.CssStyleHelper.createStyleHelper(CssStyleHelper.java:193)
>         at [javafx.graphics at 27-ea](mailto:javafx.graphics at 27-ea)/javafx.scene.Node.reapplyCss(Node.java:9996)
>         at [javafx.graphics at 27-ea](mailto:javafx.graphics at 27-ea)/javafx.scene.Node.reapplyCSS(Node.java:9959)
>         at [javafx.graphics at 27-ea](mailto:javafx.graphics at 27-ea)/javafx.scene.Scene$10.onChanged(Scene.java:1682)
>         at [javafx.base at 27-ea](mailto:javafx.base at 27-ea)/com.sun.javafx.collections.TrackableObservableList.lambda$new$0(TrackableObservableList.java:44)
>         at [javafx.base at 27-ea](mailto:javafx.base at 27-ea)/com.sun.javafx.collections.ListListenerHelper$SingleChange.fireValueChangedEvent(ListListenerHelper.java:162)
>         at [javafx.base at 27-ea](mailto:javafx.base at 27-ea)/com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:71)
>         at [javafx.base at 27-ea](mailto:javafx.base at 27-ea)/javafx.collections.ObservableListBase.fireChange(ObservableListBase.java:246)
>         at [javafx.base at 27-ea](mailto:javafx.base at 27-ea)/javafx.collections.ListChangeBuilder.commit(ListChangeBuilder.java:482)
>         at [javafx.base at 27-ea](mailto:javafx.base at 27-ea)/javafx.collections.ListChangeBuilder.endChange(ListChangeBuilder.java:541)
> 
> 
> or
> 
> 
> TooltipTest > testCssStylesheetChangeTooltip() STANDARD_ERROR
>     Exception in thread "JavaFX Application Thread" java.lang.NullPointerException: Cannot invoke "java.util.List.clear()" because "this.selectors" is null
>         at [javafx.graphics at 27-internal](mailto:javafx.graphics at 27-internal)/com.sun.javafx.css.StyleMap.getCascadingStyles(StyleMap.java:148)
>         at [javafx.graphics at 27-internal](mailto:javafx.graphics at 27-internal)/javafx.scene.CssStyleHelper.resetToInitialValues(CssStyleHelper.java:490)
>         at [javafx.graphics at 27-internal](mailto:javafx.graphics at 27-internal)/javafx.scene.CssStyleHelper.createStyleHelper(CssSt...

Michael Strauß has updated the pull request incrementally with one additional commit since the last revision:

  increase DELTA to 150

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/2066/files
  - new: https://git.openjdk.org/jfx/pull/2066/files/a46fd46e..8fe46bdf

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=2066&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=2066&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/2066.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/2066/head:pull/2066

PR: https://git.openjdk.org/jfx/pull/2066