Examine source code of Amazon Smile Redirect

{
  "manifest_version": 2,
  "name": "Smile Redirect",
  "version": "1.0",
  "description": "Redirects all amazon.com urls to smile.",
  "icons": {
    "48": "icons/redirect-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.amazon.com/*",
        "*://www.amazon.co.uk/*"
      ],
      "js": [
        "smile.js"
      ]
    }
  ]
}