Examine source code of fbtimer

{
  "description": "A pop up shows up after spending 5 min on facebook and then all every 2 min.",
  "manifest_version": 2,
  "name": "fbtimer",
  "version": "1.2resigned1",
  "icons": {
    "48": "icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.facebook.com/*"
      ],
      "js": [
        "fbtimer.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{c146ff37-5feb-4e1a-a4cb-f73755a06710}"
    }
  }
}