Examine source code of Simple URL Extender

{
  "manifest_version": 2,
  "name": "Simple URL Extender",
  "description": "Simply extend a shortened URL to its real URL by right clicking it and selecting 'Simple URL Extender'.",
  "version": "2.0",
  "permissions": [
    "contextMenus",
    "http://9inchurl.com/",
    "notifications"
  ],
  "author": "Kenneth",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "cs.js"
      ]
    }
  ],
  "icons": {
    "16": "icon16.png",
    "32": "icon32.png",
    "48": "icon48.png",
    "128": "icon128.png"
  }
}