src/vs/workbench/contrib/notebook/browser/contrib/cellStatusBar/executionStatusBarItemController.ts/NotebookStatusBarController/constructor
class NotebookStatusBarController:	constructor(
		private readonly _notebookEditor: INotebookEditor,
		private readonly _itemFactory: (vm: NotebookViewModel, cell: CellViewModel) => IDisposable
	) {
		super();
		this._observer = this._register(new NotebookVisibleCellObserver(this._notebookEditor));
		this._register(this._observer.onDidChangeVisibleCells(this._updateVisibleCells, this));

		this._updateEverything();
	}