Examine source code of CSS Peeper

{
  "manifest_version": 2,
  "name": "CSS Peeper",
  "description": "Extract CSS and build beautiful styleguides.",
  "version": "0.5.6",
  "permissions": [
    "activeTab",
    "scripting",
    "https://fonts.googleapis.com/"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "32": "logo-32.png",
    "64": "logo-64.png",
    "128": "logo-128.png",
    "512": "logo-512.png"
  },
  "browser_action": {
    "default_title": "Show me the styles!"
  },
  "content_security_policy": "script-src 'self'; object-src 'self'",
  "browser_specific_settings": {
    "gecko": {
      "id": "{1a40da5b-cfad-49bd-a001-683e6ab28128}"
    }
  }
}