src/vs/workbench/contrib/notebook/browser/viewModel/eventDispatcher.ts/NotebookEventDispatcher/emit
class NotebookEventDispatcher:	emit(events: NotebookViewEvent[]) {
		for (let i = 0, len = events.length; i < len; i++) {
			const e = events[i];

			switch (e.type) {
				case NotebookViewEventType.LayoutChanged:
					this._onDidChangeLayout.fire(e);
					break;
				case NotebookViewEventType.MetadataChanged:
					this._onDidChangeMetadata.fire(e);
					break;
				case NotebookViewEventType.CellStateChanged:
					this._onDidChangeCellState.fire(e);
					break;
			}
		}
	}