RFR: 8243115: Spurious invalidations due to bug in IntegerBinding and other classes

[Ambarish Rapte]

On Mon, 27 Apr 2020 11:43:28 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

> This fixes a bug where the first call to unbind would clear the internal invalidation listener used, resulting in subsequent unbind calls to be no-ops, unless bind was called again first.
> 
> I had to rewrite the parameterized test slightly as Parameterized will only call the parameters method once, and my new test modifies the internal state of the bindings used as parameters (by doing some unbind calls) which was making other tests fail.

Looks good to me. Tested on Windows10 and verified that not setting `observer` to `null` does not lead to any leak.
Please merge with latest master to trigger a GitHub build and test.

Under a different bug, should we implement the `dispose()` method? Track all observables in a Weak list and remove `observer` from them in `dispose()`

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PR: https://git.openjdk.org/jfx/pull/198