Examine source code of No Empty iframes

{
  "description": "Add an empty div to the body of any empty iframes.  Supplemental addon to ShadowFox.",
  "manifest_version": 2,
  "name": "No Empty iframes",
  "version": "1.2resigned1",
  "homepage_url": "https://github.com/overdodactyl/ShadowFox/tree/master/no_empty_iframes",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "no_empty_iframes.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8e046928-66d9-4f87-8a4b-e0515166b8f8}"
    }
  }
}