Examine source code of Flexible Overlay Clock

{
  "browser_action": {
    "default_icon": {
      "19": "clock-icon19.png",
      "38": "clock-icon38.png"
    },
    "default_popup": "options.html",
    "default_title": "Overlay Clock"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{96823de3-bcbd-4dd7-b810-858aa67edb66}"
    }
  },
  "content_scripts": [
    {
      "js": [
        "defaults.js",
        "clock.js"
      ],
      "matches": [
        "http://*/*",
        "https://*/*",
        "file://*/*"
      ],
      "run_at": "document_end"
    }
  ],
  "content_security_policy": "default-src 'none'; style-src 'self'; script-src 'self';",
  "description": "Displays a digital clock on a page.",
  "icons": {
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "manifest_version": 2,
  "name": "Overlay Clock",
  "options_ui": {
    "page": "options.html"
  },
  "permissions": [
    "storage"
  ],
  "short_name": "OverlayClock",
  "update_url": "http://clients2.google.com/service/update2/crx",
  "version": "0.8"
}