Examine source code of Media Downloader

{
  "manifest_version": 2,
  "name": "Media Downloader",
  "version": "1.0",
  "description": "Download images and videos from webpages.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "permissions": [
    "activeTab"
  ],
  "host_permissions": [
    "*://*.facebook.com/*",
    "*://*.fbcdn.net/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{02743a32-3e89-430c-93f6-8b3f123853dc}"
    }
  }
}