hg: openjfx/jfx/rt: 8211302: DragAndDrop no longer works with GTK3

[kevin.rushforth at oracle.com]

Changeset: 981cff5755bc
Author:    tsayao
Date:      2019-06-04 14:53 -0700
URL:       http://hg.openjdk.java.net/openjfx/jfx/rt/rev/981cff5755bc

8211302: DragAndDrop no longer works with GTK3
Reviewed-by: kcr, pbansal

! modules/javafx.graphics/src/main/native-glass/gtk/glass_dnd.cpp
! modules/javafx.graphics/src/main/native-glass/gtk/glass_dnd.h
! modules/javafx.graphics/src/main/native-glass/gtk/glass_general.cpp
! modules/javafx.graphics/src/main/native-glass/gtk/glass_general.h
+ tests/manual/dnd/DndTest.java