src/vs/editor/browser/config/elementSizeObserver.ts/ElementSizeObserver/measureReferenceDomElement
class ElementSizeObserver:	private measureReferenceDomElement(emitEvent: boolean, dimension?: IDimension): void {
		let observedWidth = 0;
		let observedHeight = 0;
		if (dimension) {
			observedWidth = dimension.width;
			observedHeight = dimension.height;
		} else if (this._referenceDomElement) {
			observedWidth = this._referenceDomElement.clientWidth;
			observedHeight = this._referenceDomElement.clientHeight;
		}
		observedWidth = Math.max(5, observedWidth);
		observedHeight = Math.max(5, observedHeight);
		if (this._width !== observedWidth || this._height !== observedHeight) {
			this._width = observedWidth;
			this._height = observedHeight;
			if (emitEvent) {
				this._onDidChange.fire();
			}
		}
	}