在JSON里加//有什么意义吗?

请问这样做有什么意义吗?
{
"//_comment1": "Some browsers will use this to enable push notifications.",
"//_comment2": "It is the same for all projects, this is not your project's sender ID",
"gcm_sender_id": "103953800507"
}

源代码是谷歌开源项目中的一个json数据https://github.com/firebase/q...