[Rev 01] RFR: 8236753: Animations do not play backwards after being stopped

[Nir Lisker]

> The private field `lastPlayFinished` is responsible for 2 cases where an animation in `STOPPED` status does not play after `play()` is called if the rate is negative:
> 
> 1. When the animation is created, it is `STOPPED` and `lastPlayFinished` is `false`. Setting a negative rate and calling `play()` will not jump to the end of the animation (in order to play it backwards) because the `if (lastPlayedFinished)` check is `false`. Creating the animation with `lastPlayFinished = true` fixes this. However, `SequentialTransitionPlayTest#testCycleReverse`'s initial state test implies that the original behavior is correct. *That test currently fails with this change.* Either the fix is reverted or the test is corrected.
> 2. When the animation is stopped (if it was not `STOPPED` already), `jumpTo(Duration.ZERO)` sets `lastPlayFinished` to `false`, which causes the same issue above with `play()`. Setting `lastPlayFinished = true` at the end `stop()` fixes this issue.
> 
> A test was added for case 2 to check that the playing head indeed jumps to the end of the animation. Without this fix, it stays at the start.
> 
> I'm still somewhat confused as to what constitutes a "last play finished". Any `jumpTo` resets `lastPlayFinished` to `false`, even if the jump is to the start/end of the animation. In this case, stopping an animation, jumping to its start/end, setting the rate to negative/positive, and playing, will do nothing as the end condition is reached immediately. This is what the behavior that was fixed for cases 1 and 2, but maybe this is also incorrect behavior for jumping to start/end.
> 
> A test app is included in the "parent" [bug](https://bugs.openjdk.java.net/browse/JDK-8210238), which also mentions a bug relating to **pausing** and playing backwards, so be mindful of it when testing.

The pull request has been updated with 1 additional commit.

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Added commits:
 - 18098da9: Fixed SequentialTransitionPlayTest.testCycleReverse test

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/82/files
  - new: https://git.openjdk.java.net/jfx/pull/82/files/3332a97f..18098da9

Webrevs:
 - full: https://webrevs.openjdk.java.net/jfx/82/webrev.01
 - incr: https://webrevs.openjdk.java.net/jfx/82/webrev.00-01

  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jfx/pull/82.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/82/head:pull/82

PR: https://git.openjdk.java.net/jfx/pull/82