Examine source code of 听蛙下载

{
  "description": "在听蛙网的音乐播放页面中下载对应的MP3文件。",
  "author": "chenjs",
  "manifest_version": 2,
  "name": "听蛙下载",
  "version": "1.7.3",
  "icons": {
    "48": "icons/tw-48.png",
    "96": "icons/tw-96.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "downloads",
    "notifications",
    "*://*.itingwa.com/listen/*"
  ],
  "page_action": {
    "default_icon": {
      "48": "icons/tw-48.png",
      "96": "icons/tw-96.png"
    },
    "show_matches": [
      "*://*.itingwa.com/listen/*"
    ]
  }
}