src/vs/workbench/contrib/notebook/browser/viewParts/notebookOverviewRuler.ts/NotebookOverviewRuler/constructor
class NotebookOverviewRuler:	constructor(readonly notebookEditor: INotebookEditorDelegate, container: HTMLElement, @IThemeService themeService: IThemeService) {
		super(themeService);
		this._domNode = createFastDomNode(document.createElement('canvas'));
		this._domNode.setPosition('relative');
		this._domNode.setLayerHinting(true);
		this._domNode.setContain('strict');

		container.appendChild(this._domNode.domNode);

		this._register(notebookEditor.onDidChangeDecorations(() => {
			this.layout();
		}));

		this._register(browser.PixelRatio.onDidChange(() => {
			this.layout();
		}));
	}