This PR fixes the implementation of `ControlUtils.reducingChange`, which incorrectly computed adjacent removed indices, thus resulting in incorrect removal notifications.
Since there were no unit tests for this method, I also added a bunch of tests. After applying this fix, I can no longer reproduce [JDK-8189354](https://bugs.openjdk.java.net/browse/JDK-8189354) and [JDK-8189228](https://bugs.openjdk.java.net/browse/JDK-8189228). ------------- Commit messages: - Fix incorrect change notifications for removed items - Failing tests Changes: https://git.openjdk.java.net/jfx/pull/480/files Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=480&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8189354 Stats: 194 lines in 4 files changed: 175 ins; 9 del; 10 mod Patch: https://git.openjdk.java.net/jfx/pull/480.diff Fetch: git fetch https://git.openjdk.java.net/jfx pull/480/head:pull/480 PR: https://git.openjdk.java.net/jfx/pull/480
