Examine source code of URLCompress

{
  "manifest_version": 2,
  "name": "URLCompress",
  "version": "0.0.3",
  "description": "Little utility for URL shortening with is.gd.",
  "author": "Michal Tvrznik",
  "permissions": [
    "http://*/*",
    "https://*/*",
    "tabs"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "icons": {
    "128": "icon.png"
  },
  "applications": {
    "gecko": {
      "id": "URLCompress@xpi"
    }
  }
}