src/vs/workbench/browser/dnd.ts/CompositeDragAndDropObserver/writeDragData
class CompositeDragAndDropObserver:	private writeDragData(id: string, type: ViewType): void {
		this.transferData.setData([type === 'view' ? new DraggedViewIdentifier(id) : new DraggedCompositeIdentifier(id)], type === 'view' ? DraggedViewIdentifier.prototype : DraggedCompositeIdentifier.prototype);
	}