Examine source code of Canonical Url Detector

{
  "manifest_version": 2,
  "name": "Canonical Url Detector",
  "description": "__MSG_appDesc__",
  "default_locale": "en",
  "version": "1.3.2",
  "author": "irok",
  "homepage_url": "https://chrome.google.com/webstore/detail/dcbmeicnoejpldipejlefojiiebhogij",
  "icons": {
    "16": "img/icon-canonical.png",
    "48": "img/icon-48.png",
    "128": "img/icon-128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "page_action": {
    "default_icon": {
      "16": "img/icon-canonical.png"
    },
    "default_title": "Canonical Url Detector"
  },
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "permissions": [
    "webNavigation"
  ]
}