Examine source code of IAteThis

{
  "manifest_version": 2,
  "name": "IAteThis",
  "version": "1.1",
  "description": "Calorie info downloader by Sparksammy that works with CalorieKing to track what you ate.",
  "icons": {
    "48": "icons/iat-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.calorieking.com/*/*/foods/f/*"
      ],
      "js": [
        "iatethis.js"
      ]
    }
  ]
}