src/vs/workbench/contrib/notebook/browser/contrib/cellStatusBar/contributedStatusBarItemController.ts/ContributedStatusBarItemController/constructor
class ContributedStatusBarItemController:	constructor(
		private readonly _notebookEditor: INotebookEditor,
		@INotebookCellStatusBarService private readonly _notebookCellStatusBarService: INotebookCellStatusBarService
	) {
		super();
		this._observer = this._register(new NotebookVisibleCellObserver(this._notebookEditor));
		this._register(this._observer.onDidChangeVisibleCells(this._updateVisibleCells, this));

		this._updateEverything();
		this._register(this._notebookCellStatusBarService.onDidChangeProviders(this._updateEverything, this));
		this._register(this._notebookCellStatusBarService.onDidChangeItems(this._updateEverything, this));
	}