Examine source code of urlshort

{
  "name": "urlshort",
  "short_name": "urlshort",
  "version": "0.1.0",
  "description": "URL shortener plugin to allow \"go/shortcut\" in the URL bar",
  "omnibox": {
    "keyword": "go"
  },
  "background": {
    "scripts": [
      "build/urlshort.js"
    ]
  },
  "icons": {
    "16": "icons/arrow-boxed-flat/16x16.png",
    "32": "icons/arrow-boxed-flat/32x32.png",
    "64": "icons/arrow-boxed-flat/64x64.png",
    "128": "icons/arrow-boxed-flat/128x128.png",
    "256": "icons/arrow-boxed-flat/256x256.png",
    "512": "icons/arrow-boxed-flat/512x512.png"
  },
  "manifest_version": 2,
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "*://www.google.com/",
    "*://www.google.no/",
    "*://www.google.se/",
    "*://www.google.dk/",
    "*://go/",
    "*://www.bing.com/",
    "*://duckduckgo.com/"
  ]
}