src/vs/workbench/contrib/markers/browser/markersTreeViewer.ts/ResourceDragAndDrop/getDragLabel
class ResourceDragAndDrop:	getDragLabel?(elements: MarkerElement[]): string | undefined {
		if (elements.length > 1) {
			return String(elements.length);
		}
		const element = elements[0];
		return element instanceof ResourceMarkers ? basename(element.resource) : undefined;
	}