Examine source code of Centurial

{
  "name": "Centurial",
  "description": "Saves web sites to Centurial as a source.",
  "version": "1.1.1",
  "manifest_version": 2,
  "permissions": [
    "activeTab",
    "nativeMessaging",
    "<all_urls>",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Save to Centurial",
    "default_icon": {
      "16": "images/icon 16x16.png",
      "32": "images/icon 32x32.png",
      "48": "images/icon 48x48.png",
      "64": "images/icon 64x64.png",
      "128": "images/icon 128x128.png"
    }
  },
  "icons": {
    "16": "images/icon 16x16.png",
    "32": "images/icon 32x32.png",
    "48": "images/icon 48x48.png",
    "64": "images/icon 64x64.png",
    "128": "images/icon 128x128.png"
  },
  "applications": {
    "gecko": {
      "id": "firefox-connector@centurial.net"
    }
  }
}