[Rev 02] RFR: 8225571: Port DND source to use GTK instead of GDK

[Thiago Milczarek Sayao]

> https://bugs.openjdk.java.net/browse/JDK-8225571
> 
> To run tests (on the root of the source tree):
> ./gradlew apps
> java @build/run.args -cp apps/toys/DragDrop/dist/DragDrop.jar dragdrop.DragDropWithControls
> java @build/run.args -cp apps/toys/DragDrop/dist/DragDrop.jar dragdrop.DragDropColor
> 
> java -Djdk.gtk.version=2 @build/run.args -cp apps/toys/DragDrop/dist/DragDrop.jar dragdrop.DragDropWithControls
> java -Djdk.gtk.version=2 @build/run.args -cp apps/toys/DragDrop/dist/DragDrop.jar dragdrop.DragDropColor

The pull request has been updated with 1 additional commit.

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

Added commits:
 - 554734c0: Remove blank line

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/4/files
  - new: https://git.openjdk.java.net/jfx/pull/4/files/d16fc2c6..554734c0

Webrevs:
 - full: https://webrevs.openjdk.java.net/jfx/4/webrev.02
 - incr: https://webrevs.openjdk.java.net/jfx/4/webrev.01-02

  Stats: 3 lines in 3 files changed: 0 ins; 1 del; 2 mod
  Patch: https://git.openjdk.java.net/jfx/pull/4.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/4/head:pull/4

PR: https://git.openjdk.java.net/jfx/pull/4