On editor.setData() native listeners are detached, but document stays so CKE listeners stop working

[Piotrek Koszuliński]

1. Open any sample with wysiwygarea.
2. CKEDITOR.instances.editor1.document.on( 'click', function() { console.log( 'click1' ) } );
3. Test that it works. OK.
4. CKEDITOR.instances.editor1.setData( 'xxx' );
5. Test that the click listener no longer works. OK.
6. CKEDITOR.instances.editor1.document.on( 'click', function() { console.log( 'click2' ) } );
7. Test that it works. NOK.

In general - if listener to some event was attached before set data, then it will no longer work after setting data and it won't be possible to attach a new one.

The reason is that setting data (unlike switching modes) keeps the same document, but writing to that document removes all its previous listeners.

On every domObject.on() we push the listener to domObject.getCustomData( '_' ) listeners repository and if a native listener has not been added yet we add it to the native element.

Since setting data keeps the same document, the custom data (our listeners repository) stays the same. But the native listeners are removed. This means that when trying to add a new listener editor thinks that a native listener was already added, because the listeners repository already contains an entry for that event.

The solution will be to clear events repository on set data.