fix: Ensure DocumentContentSynchronizer is always disposed

[eliseevh]

Fixes #1360

[angelozerr]

Thanks so much @eliseevh !

Let me try your PR

[angelozerr]

Why you have removed removeDocumentListener ?

[eliseevh]

Because I changed call to addDocumentListener, so it would be automatically removed when synchronizer is disposed (it is important to call Disposer.dispose instead of directly calling dispose method on synchronizer). This way, document listener would be also removed if synchronizer is disposed in other places

[angelozerr]

I am sorry I don't understand very well.

document.addDocumentListener(synchronizer, synchronizer); is done but what about

document.removeDocumentListener(synchronizer);

You mean that line code Disposer.dispose(synchronizer); will remove synchronizer from document listener?

[eliseevh]

Yes. addDocumentListener(Document listener, Disposable) docs says that when second argument is disposed, it will remove document listener (you can look into implementation, it is probably something like addDocumentListener(listener); Disposer.register(disposable, () -> removeDocumentListener(listener));)
And if you register some disposable with Disposer.register(parent, child), when parent is disposed with Disposer.dispose, it will automatically dispose child, so it will remove document listener

[angelozerr]

Good catch! I have verified this behavior.

Before calling Disposer.dispose:

After calling Disposer.dispose:

[angelozerr]

Thanks so much @eliseevh !