src/vs/workbench/contrib/files/browser/views/openEditorsView.ts/OpenEditorsDragAndDrop/getDragLabel
class OpenEditorsDragAndDrop:	getDragLabel?(elements: (OpenEditor | IEditorGroup)[]): string {
		if (elements.length > 1) {
			return String(elements.length);
		}
		const element = elements[0];

		return element instanceof OpenEditor ? element.editor.getName() : element.label;
	}