src/vs/workbench/browser/parts/views/treeView.ts/AbstractTreeView/getOptimalWidth
class AbstractTreeView:	getOptimalWidth(): number {
		if (this.tree) {
			const parentNode = this.tree.getHTMLElement();
			const childNodes = ([] as HTMLElement[]).slice.call(parentNode.querySelectorAll('.outline-item-label > a'));
			return DOM.getLargestChildWidth(parentNode, childNodes);
		}
		return 0;
	}