src/vs/editor/browser/viewParts/overviewRuler/decorationsOverviewRuler.ts/DecorationsOverviewRuler/constructor
class DecorationsOverviewRuler:	constructor(context: ViewContext) {
		super(context);

		this._domNode = createFastDomNode(document.createElement('canvas'));
		this._domNode.setClassName('decorationsOverviewRuler');
		this._domNode.setPosition('absolute');
		this._domNode.setLayerHinting(true);
		this._domNode.setContain('strict');
		this._domNode.setAttribute('aria-hidden', 'true');

		this._updateSettings(false);

		this._tokensColorTrackerListener = TokenizationRegistry.onDidChange((e) => {
			if (e.changedColorMap) {
				this._updateSettings(true);
			}
		});

		this._cursorPositions = [];
	}