Examine source code of Show IP

{
  "manifest_version": 2,
  "name": "Show IP",
  "short_name": "Show IP",
  "version": "2.4",
  "description": "This extension allows you to display the public IP address.",
  "icons": {
    "32": "images/ip-32.png",
    "48": "images/ip-48.png",
    "64": "images/ip-64.png",
    "128": "images/ip-128.png"
  },
  "permissions": [
    "tabs",
    "<all_urls>",
    "http://*/*",
    "https://*/*"
  ],
  "browser_action": {
    "default_icon": {
      "64": "images/icon.png"
    },
    "default_title": "Show IP",
    "default_popup": "html/browserinfo.html"
  }
}