`EventHandler` property implementations in `Scene` and `Window` use anonymous classes derived from `ObjectPropertyBase`. We can remove about 650 lines of boilerplate code by using a common property class instead.
------------- Commit messages: - use EventHandlerProperty Changes: https://git.openjdk.org/jfx/pull/1819/files Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1819&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8358255 Stats: 793 lines in 2 files changed: 50 ins; 694 del; 49 mod Patch: https://git.openjdk.org/jfx/pull/1819.diff Fetch: git fetch https://git.openjdk.org/jfx.git pull/1819/head:pull/1819 PR: https://git.openjdk.org/jfx/pull/1819
