src/vs/workbench/browser/dnd.ts/CompositeDragAndDropObserver/INSTANCE
class CompositeDragAndDropObserver:	static get INSTANCE(): CompositeDragAndDropObserver {
		if (!CompositeDragAndDropObserver.instance) {
			CompositeDragAndDropObserver.instance = new CompositeDragAndDropObserver();
		}

		return CompositeDragAndDropObserver.instance;
	}