Examine source code of Fun Arcade

{
  "manifest_version": 2,
  "name": "Fun Arcade",
  "description": "Play Arcade Games!",
  "version": "1.2",
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "window.html"
  },
  "permissions": [
    "activeTab",
    "tabs",
    "contextMenus",
    "http://*.freearcade.net/"
  ],
  "background": {
    "persistent": false,
    "scripts": [
      "contextmenu.js"
    ]
  },
  "content_scripts": [
    {
      "js": [
        "domMan.js"
      ],
      "matches": [
        "http://*.freearcade.net/*"
      ],
      "run_at": "document_end"
    }
  ],
  "icons": {
    "16": "icon.png",
    "48": "icon.png",
    "128": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f4e41784-b5b6-4c35-a036-ee3711ae773e}"
    }
  }
}