src/vs/base/browser/ui/scrollbar/abstractScrollbar.ts/AbstractScrollbar/_createArrow
class AbstractScrollbar:	protected _createArrow(opts: ScrollbarArrowOptions): void {
		const arrow = this._register(new ScrollbarArrow(opts));
		this.domNode.domNode.appendChild(arrow.bgDomNode);
		this.domNode.domNode.appendChild(arrow.domNode);
	}