function _handleRelatedDocumentDeleted(url) {
        var liveDoc = _relatedDocuments[url];
        if (liveDoc) {
            delete _relatedDocuments[url];
        }

        if (_server) {
            _server.remove(liveDoc);
        }
        _closeDocument(liveDoc);
    }
Removes the given CSS/JSDocument from _relatedDocuments. Signals that the
given file is no longer associated with the HTML document that is live (e.g.
if the related file has been deleted on disk).
@param {string} url Absolute URL of the related document