src/vs/editor/browser/controller/mouseTarget.ts/HitTestContext/_findAttribute
class HitTestContext:	private static _findAttribute(element: Element, attr: string, stopAt: Element): string | null {
		while (element && element !== document.body) {
			if (element.hasAttribute && element.hasAttribute(attr)) {
				return element.getAttribute(attr);
			}
			if (element === stopAt) {
				return null;
			}
			element = <Element>element.parentNode;
		}
		return null;
	}