Examine source code of Lenny Face Generator

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "name": "Lenny Face",
  "description": "this is a lenny face generator simple to use",
  "version": "2.1",
  "browser_action": {
    "default_icon": "images/icon.png",
    "default_popup": "popup.html"
  },
  "icons": {
    "16": "images/icon.png",
    "32": "images/icon.png",
    "48": "images/icon.png",
    "128": "images/icon.png"
  },
  "permissions": [
    "activeTab"
  ]
}