hg: openjfx/jfx-dev/rt: 8204856: WebEngine document becomes null after PAGE_REPLACED event

[arunprasad.rajkumar at oracle.com]

Changeset: 01a04d558b99
Author:    arajkumar
Date:      2018-07-05 12:12 +0530
URL:       http://hg.openjdk.java.net/openjfx/jfx-dev/rt/rev/01a04d558b99

8204856: WebEngine document becomes null after PAGE_REPLACED event
Reviewed-by: mbilla, kcr

! modules/javafx.web/src/main/java/javafx/scene/web/WebEngine.java
! modules/javafx.web/src/test/java/test/javafx/scene/web/HistoryStateTest.java