Examine source code of Close This Page

{
  "manifest_version": 2,
  "name": "Close This Page",
  "version": "1.0",
  "description": "In the context menu to close the current webpage.",
  "icons": {
    "32": "close.png"
  },
  "permissions": [
    "menus",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{70a3f4d7-aedd-460b-8332-77b71bd08932}"
    }
  }
}