Adds `MOUSE_DRAG_DONE` event type to `MouseDragEvent` and appropriate handlers.
------------- Commit messages: - Initial commit Changes: https://git.openjdk.org/jfx/pull/1873/files Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1873&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8365635 Stats: 98 lines in 5 files changed: 90 ins; 3 del; 5 mod Patch: https://git.openjdk.org/jfx/pull/1873.diff Fetch: git fetch https://git.openjdk.org/jfx.git pull/1873/head:pull/1873 PR: https://git.openjdk.org/jfx/pull/1873
