src/vs/editor/browser/config/elementSizeObserver.ts/ElementSizeObserver/constructor
class ElementSizeObserver:	constructor(referenceDomElement: HTMLElement | null, dimension: IDimension | undefined) {
		super();
		this._referenceDomElement = referenceDomElement;
		this._width = -1;
		this._height = -1;
		this._resizeObserver = null;
		this.measureReferenceDomElement(false, dimension);
	}