src/vs/workbench/browser/parts/editor/editorGroupView.ts/EditorGroupView/shouldRestoreFocus
class EditorGroupView:	private shouldRestoreFocus(target: Element): boolean {
		const activeElement = document.activeElement;

		if (activeElement === document.body) {
			return true; // always restore focus if nothing is focused currently
		}

		// otherwise check for the active element being an ancestor of the target
		return isAncestor(activeElement, target);
	}