Examine source code of Grouper

{
  "manifest_version": 2,
  "name": "Grouper",
  "version": "1.0",
  "description": "A grouper which can group your tabs automatically when you use search engine.",
  "icons": {
    "16": "images/icon16.png",
    "48": "images/icon48.png",
    "128": "images/icon128.png"
  },
  "background": {
    "scripts": [
      "Grouper.js"
    ]
  },
  "permissions": [
    "tabs",
    "http://*/*",
    "https://*/*"
  ]
}